NUT BREEDING

H. L. CRANE, Principal Horticulturist,
C. A. REED, Associate Pomologist, and
M. N. WOOD, Pomologist, Division of Fruit and Vegetable Crops and Diseases, Bureau of Plant Industry

[ABSTRACT.]  WHEN the chestnut blight wiped out this magnificent eastern forest tree in the early part of the present century, chestnut breeding became a pressing need. The most promising of all material at present is the Chinese chestnut. It is much more blight-resistant than any others, and the nuts combine the large size of the European chestnut with the sweetness of the American. The Japanese chestnut, which has considerable blight resistance, unfortunately produces nuts that are usually negative in flavor, but it may be useful in breeding. Selection and hybridization are being actively carried on by the Department of Agriculture with the object of developing varieties for both commercial and home growing that will be resistant to blight and if possible to weevils, and hardy enough to grow throughout the chestnut range; bear heavy annual crops, beginning at a fairly young age; bear not more than three rather large nuts to the bur, which must separate automatically; have fine texture, good flavor, and good keeping quality; be attractive in appearance and not subject to shell splitting; and have an inner skin or pellicle that will not adhere to the kernel.

Improvement in nuts by some sort of selection was probably brought about originally by cave men, wild animals, and birds. The more toothsome nuts were the ones chiefly sought after and carried from place to place or hidden in caches. Weaker creatures, forced by stronger rivals from warmer and more comfortable localities, were obliged to steal their food and carry it to places safer for themselves although often less favorable for the nuts, which they might lose, to take root and thrive. It was by such means that the productive areas were gradually expanded and greater hardiness and ability to grow at higher or lower altitudes were developed. Ocean currents, which have much to do with the distribution of many kinds of seeds, appear to have had little part in the carrying of Temperate Zone nuts from place to place.

Planters have as yet made little systematic effort to breed superior varieties of any kind of nuts by hybridization. This is doubtless because of the great abundance of wild nuts that in the past could be had for the gathering, and more recently because of the practical difficulties standing in the way of tree breeding, especially the time required to complete the cycle of a generation. The countless centuries of crude selection through which such cultivated forms as filberts, almonds, Persian (English) walnuts, and European chestnuts have passed have tended so to fix the types that to a large extent they now come fairly true to type from seed, although in this country none but grafted trees of selected varieties are planted, except when only seedlings are to be had. Most of the nuts now on the world market are from seedling trees. The extensive multiplication of superior varieties resulting from selective or controlled breeding is still greatly handicapped by practical difficulties in propagation, especially in the case of the more difficult species of walnut and hickory.

CHESTNUT

Chestnut improvement in this country has developed along four distinct lines—by selection from native seedlings, by the introduction of Old World species and the continuance of selection with them, by natural hybridization among various species and varieties when grown together, and by controlled hybridization, the newest and most promising method.

Breeding by selection from native species has contributed little, as few varieties developed by this method have become prominent.  The majority so originated are now obsolete, and it would probably be impossible to establish the purity of the supposed American parentage of the very few still grown by nurserymen. Numbers of hybrids exist that are plainly the result of natural crossing between native species, but none has commercial value.

Because the American chestnut is very susceptible to what is known as blight, a fatal fungus disease from the Orient, which was first discovered in this country in 1904 and has since spread over practically the entire East, the chief interest in chestnut planting now lies in the use of species from the Old World.

Altogether eight species of chestnuts, including the closely related chinquapins, have been used in the chestnut developments of this country. Formerly the most important and abundant of these species was the American chestnut, Castanea dentata (Marsh.) Borkh. This had a natural range extending from lower New England westward to southeastern Michigan and southward to northern Georgia and eastern Arkansas. As a tree it was one of the largest growing species of the Eastern States; a trunk diameter of 6 to 7 feet and a limb spread of 50 or more feet from the center of the tree were not uncommon with trees standing in the open. As a forest tree it was once a dominant species over large mountain areas of the Appalachian Range from Pennsylvania south to the Carolinas and eastern Tennessee. In these regions a height of more than 100 feet with a diameter at the base of not more than 2 to 3 feet was common. The trees were much sought after as material for telephone poles, fence rails, mine props, and other similar purposes where important factors were abundance, uniformity of size, freedom from knots, ease of splitting, and durability both above and below ground.

The burs of the American chestnut are relatively large and the spines long and compound. The nuts are coated at the apex, or nearly to the middle, with thick, pale down. The kernels are very sweet and palatable. Selected nuts of this species are among the most delicious of any known. They were thought to be the choicest of all chestnuts until the arrival of certain oriental strains, which proved to be their equal.

Two other species of Castanea are indigenous to this country. Both are chinquapins and therefore not true chestnuts, although closely related. These are much alike and are restricted to more limited ranges than the American chestnut. The trees are dwarfish or shrubby in habit, and the nuts are borne singly in small burs, which form in racemes or long, stringlike clusters. The nuts are small but very sweet. The better known of the two species is the tree or common chinquapin, C. pumila (L.) Mill. This occurs chiefly in the Southeast, from central Pennsylvania to Florida and west to Texas. The species occasionally forms hybrids with the American chestnut. One such hybrid tree was found, probably about 1895, by the late J. G. Rush, of West Willow, Pa. This was propagated and disseminated to some extent by Rush, after whom it had been named, but after a few years of experimentation he cut down the trees as he came to regard the variety as merely a novelty of little practical value. However, trees are still grown by some who find it an interesting form of considerable value for home use. The other species of chinquapin is the so-called alder-leaved or trailing chinquapin, C. alnifolia Nutt., a low-growing shrub confined to certain localities in the South Atlantic States and occurring rarely as far west as central Louisiana. This species has the peculiarity of reproducing itself by means of underground stems and forming dense thickets.

DEVELOPMENTS FROM EARLY INTRODUCTIONS

The first foreign chestnut introduced into this country was the European or Spanish chestnut, Castanea sativa Mill. The earliest record that has so far come to light appears in the notes of Thomas Jefferson, according to Bailey (5), and shows that scions of a “French chestnut" were grafted by him in 1773 at his home, Monticello, near Charlottesville, Va. This species also is a large tree, growing in Europe to 100 feet in height and 30 feet in circumference, though in this country it seldom grows larger than a medium-sized apple tree. The trees are precocious and under American conditions very fruitful. The nuts are large and usually very good but rarely equal in quality to the average American chestnut. The tree is scarcely less fatally subject to blight than the American chestnut and therefore is not longer being planted in blight-affected zones.

The second foreign species to become important in this country was the Japanese chestnut, Castanea crenata Sieb. and Zucc. This is a relatively small tree or shrub growing to 30 feet in height. The species is characterized by small stiff leaves, great fruitfulness, and large size of nuts, which are sometimes enormous. Occasionally the nuts are very good but as a rule the flavor is mild or neutral and the texture somewhat coarse. Quite commonly the pellicle or skin covering the kernel is thick or even woody. It may adhere tightly and be removable only by paring with a knife. The species is quite resistant to blight, although in the experience of the Division of Forest Pathology, Bureau of Plant Industry, United States Department of Agriculture, it is exceeded somewhat in this respect by the Chinese or hairy chestnut (C. mollissima Bl.)

The Chinese chestnut tree is intermediate in size between the European species as grown in this country and the American species. It was known in the United States to a slight extent as early as 1853, but it may be said to have been introduced by the Department of Agriculture in 1907. While very young it tends to develop many lateral branches with little tendency toward a central leader. Later on it assumes more definite shape and becomes a standard tree. It begins bearing relatively early and is sometimes highly prolific. The outstanding feature of this species, in addition to the fact that it is apparently more resistant to blight than any other, is the excellence of the nuts, many of which are as large as the European and as sweet as the best American nuts. They are attractive in appearance, often being of a rich mahogany brown and frequently glossy. There is little down on the surface and that only at the apex. When in the proper stage of maturity the pellicle of the kernels tends to adhere to the shells rather than the kernels.

In 1799 Irenée du Pont came to New Jersey from France and “after a residence at Bergen Point, where he took much pleasure in propagating a number of European seeds and plants received from France, removed to Delaware in 1802 and settled on the Brandywine, where he established the famous Du Pont Powder Mills” (26). At both places Du Pont paid special attention to bringing European chestnuts into this country, chiefly from his native home, and to disseminating both these and their offspring among his friends and acquaintances. Records show that many varieties of European chestnuts, which during the eighties and nineties became prominent in this country, were derived from Du Pont introductions.

Powell (26) records that scions taken from one of the Du Pont trees and grafted in 1850 on stocks of the native species gave rise to a variety named Darlington, after Thomas Darlington, of West Chester, Pa., who was instrumental in disseminating the variety. This may have been the first chestnut grafting in this country after that of Jefferson.

Beginning in the early eighties and continuing for about two decades, a large number of seedlings of European species were named and propagated. Some of these were popularly supposed to have been hybrids with the American species, but this was not proved. A few were extensively used in top-working coppice growth in cut-over chestnut forest lands of eastern Pennsylvania, New Jersey, northern Maryland, and northern Virginia. All proved to be fatally susceptible to blight. The best-known varieties were Paragon, Numbo, Ridgeley, Cooper, and Scott. These are now rarely grown and are found only in districts outside of blight-affected zones. Even there they are being replaced by better varieties.

A more recent group of varieties, thought by some to be partially or entirely European in origin, although regarded by the originator as pure American, was developed by the late E. A. Riehl, of Godfrey, Ill., from seedlings of unknown origin obtained from the nursery of Charles A. Green, Rochester, N. Y., and planted about 1890. To hasten the trees into early bearing Riehl grafted scions from them into the top of an old seedling American chestnut. The resulting nuts so impressed him that he named the variety Rochester. From Rochester seedlings he selected and named a number of still better varieties such as Progress, Fuller, Champion, and Van Fleet. Gibbens, from the same source, has been added since Riehl’s death in 1924. However, these varieties, like all others having either European or American parentage, are very susceptible to blight, and when once affected the trees perish quickly.

The Japanese chestnut, Castanea crenata, has also been a source of numerous varieties having desirable characteristics. According to Fuller (14), the earliest recorded introduction of this species took place in 1876, when a number of trees were received by S. B. Parsons & Co., nurserymen at Flushing, N. Y., from Thomas Hogg, a skilled horticulturist of this country who spent several years in Japan collecting rare kinds of trees and shrubs. These trees fruited in 1878 and soon attracted attention on account of the large size and excellent quality of the nuts and their precocious bearing habits. According to Powell (26), "Parson’s Japan” was well known for a few years, but presently disappeared.

In 1882 the late William Parry, of Parry, N. J., imported 1,000 grafted trees from Japan, and from them a single tree, the Parry, was finally selected and became the progenitor of many varieties. In 1886 Luther Burbank, of Santa Rosa, Calif., planted large Japanese chestnuts collected for him in Japan, and from over 10,000 bearing seedlings he selected 3 as worthy of perpetuation—Hale, Coe, and McFarland. In 1915 he introduced another variety, Miracle, also of Japanese origin. Groups of Japanese varieties were developed by J. W. Kerr, Denton, Md., and J. W. Killen, Felton, Del., probably from seed procured from Parry or other importers. Each of these men introduced a considerable number of carefully chosen varieties, of which Black, Felton, Kent, Kerr, Killen, and Martin are still being grown occasionally on the Chesapeake Peninsula.

Developments and extensive plantings of Japanese and European chestnut varieties made from 30 to 40 years ago included those of the Albion Chestnut Co. at Clementon, N. J.; the Mammoth Chestnut Co. and Joseph Williams at Riverton, N. J.; Joseph, T. Lovett at Emilie, Pa.; the Paragon Nut & Fruit Co., Lancaster, Pa.; and C. K. Sober, Lewisburg, Pa.

BREEDING BY HYBRIDIZATION

Chestnut breeding by controlled cross-pollination appears to have been the first work of the kind undertaken in this country, if not in the world, with any species of nut, and a number of apparently good varieties were so developed. Unfortunately, chestnut blight entered from the Orient at about the time the hybrids were ready to be introduced, and none proved to have sufficient resistance to this disease to justify extensive planting. This early work was undertaken almost simultaneously by two men wholly unknown to each other and living in remote sections of the country. Both died about the time that material was becoming available with which the next steps in breeding and the development of blight-resistant varieties might have been taken.

The first work appears to have been that begun in 1888 by George W. Endicott, of Villa Ridge, Ill., a veteran of the Civil War, farmer, and practical fruit grower. In that year he began a search for an American chestnut tree blossoming early enough to furnish pollen for use on the pistillate flowers of the Giant (Japan Giant) variety (39), which was prolific but not of high grade. It was as a result of such a cross made by him in 1895 that he developed the Boone variety.

The next hybridizing work with chestnuts began in 1894 when Van Fleet (43) well known in this country as a breeder of roses and small fruits, who was then an associate editor of the Rural New Yorker, dusted pollen of a native chestnut on the pistillate flowers of Paragon, a popular variety of European parentage. The resulting seedlings were grown on the private grounds of Van Fleet in Little Silver, N.J. Coming into bearing in 1906, they: showed unmistakable signs of hybridity and might have become valuable had they not been seriously attacked by chestnut blight a year or so after beginning to fruit.

The period of Van Fleet’s most important work in chestnut breeding began in 1900. Between then and the time of his death in 1921 he made thousands of crosses, using many species and growing hybrids through several successive generations. His earlier work largely consisted of crossing the native chinquapin, Castanea pumila, with such leading European varieties as Numbo and Paragon and such Japanese sorts as Parry (Parry’s Giant), Killen, and Hale. To some extent he also used pollen from native wild trees of the American chestnut. In his later work he included the Chinese chestnut, C. mollissima.

The final results of Van Fleet’s work were practically nil, so far as production of commercial varieties was concerned, for the reason that all hybrids having any degree of either American or European parentage proved susceptible to blight and soon succumbed. However, one hybrid, designated as S-8 from its position in the orchard, and believed to have been the result of a cross of chinquapin with Japanese chestnut, is being tested under controlled infection conditions for possible resistance. Recent reports indicate that this hybrid is not sufficiently resistant to blight to justify general planting.

The work of both Endicott and Van Fleet is important because it gave information as to the possibility of using different species in breeding and it developed a useful technique.

The chestnut breeding of Van Fleet has been continued and expanded by the Division of Forest Pathology of the Bureau of Plant Industry with G. F. Gravatt and R. B. Clapper in charge. Thousands of crosses have been made involving the eight species, and the work has been carried through several successive generations. Selections are now being made of the most promising individuals for varietal use.

DEFECTS AND MERITS OF PRESENT VARIETIES

Present varieties of the chestnut have many serious defects, of which susceptibility to certain natural enemies is most prominent. One of these enemies is chestnut blight, the fungus disease already referred to as attacking all species in varying degrees. It has spread rapidly over the native range of the chestnut since it was first discovered on Long Island early in the present century. It is most serious with the American and next with the European chestnut. Japanese varieties and seedlings are resistant. Varieties of the Chinese chestnut, Castanea mollissima, appear to be even more resistant, and as the nuts are generally superior to those of the Japanese chestnut, the species appears to offer greater promise for orchard planting.

Chestnut weevils are native pests attacking all choice varieties with about equal severity. If any chestnuts are less subject to this menace than others they are the largest and least palatable of those from Japan. The adult weevil deposits its eggs deep in the immature kernel when the nut is partially grown. One egg or many may be placed in each nut. They hatch at about the time the nuts ripen, and the larvae feed and fatten inside the nut, then bore their way out and enter the ground for the winter stage. In early-ripening varieties these insects often do not appear until after the nuts have arrived in the market. A few days later, especially if the weather is warm, and about the time the nuts reach the consumer, the white larvae or grub- like insects emerge. In severe infestations these pests will be seen crawling in all directions, or if a nut is cut open they will be found in various parts of the kernel, to the disgust of the would-be consumer.

Whether blight, which may completely kill the tree and end the story, or weevils, which do not affect the tree but ruin the nuts after they are grown, is the more seriously limiting factor in chestnut growing is an open question. No method of spraying has been found sufficiently effective with either to be worth while. However, as already stated, the blight-resistant Chinese and Japanese species appear to offer a practical solution to the former evil, and to some extent planting chestnut trees only in thickly populated poultry yards is being found successful in controlling the latter. One way of avoiding weevil damage would be to plant only in parts of the country where this pest is not known to be present. As time goes on, more satisfactory means of controlling or obviating both of these natural enemies may be developed.

Other defects of chestnuts are tardy bearing; shy bearing or over- productiveness; lateness in time of maturity; failure of the burs to open and discharge the nuts automatically; variability in size of nuts; a tendency for the shells to split badly and thus expose the kernel to weather; thickness of pellicle; tight adherence of pellicle to the kernel; and coarseness, lack of sweetness, and poor keeping qualities. No known varieties are free from all of these objectionable features. With some exceptions, the American chestnut bears nuts that are small and unattractive in appearance, and the pellicle of the kernel adheres tightly, although it is so thin as not to be objectionable. The trees grow to immense size but are tardy in beginning to bear and seldom bear heavily. Besides being fatally subject to blight, the European chestnut is usually of medium flavor, the pellicle adheres tightly to the kernel, and the texture is seldom as fine as that of the American and Chinese species. The chief defects of the Japanese chestnut are poor flavor and coarseness of kernel, thickness and even woodiness of pellicle, and usually tight adherence of pellicle to kernel. As a rule Japanese chestnuts are good to eat only when cooked. The Chinese chestnut also has its defects, but owing to its newness in this country it has not yet been fully appraised. As already noted, it is subject to weevils and somewhat so to blight. Young trees are slow in assuming distinct tree form. While of nursery age the little trees are very subject to winter injury. Nothing is known as to the self-sterility or inter-sterility of Chinese varieties. Very few have yet been named and none has been thoroughly tested. The real merits and defects of this species can be determined only by wide observation over a period of years.

The good characteristics of chestnuts are fairly well distributed among the various species and varieties. The American chestnut makes the largest and most upright tree, is by far the best for timber purposes, and the kernels are the most uniformly sweet. The European chestnut bears well and annually, beginning at a moderately early age. The tree does not ordinarily assume such great, size as to be objectionable to the orchardist. The nuts are of good commercial size, and those of some varieties are sweet and highly palatable. Nuts of this species often bring top prices. The Japanese chestnut is outstanding in its normal precocity, prolificacy, habit of annual bearing, and large size and attractive appearance of the nuts. The species is highly resistant to blight and would need only the sweetness, fineness of texture, and palatability of the best American and Chinese chestnuts, and the automatic separation of pellicle from kernel, characteristic of some of the latter, to rank among the favorites with both growers and consumers. There are a few Japanese varieties of such merit as to give promise of orchard usefulness.

As a rule, all chestnuts are more or less self-sterile and bear better when interplanted with other varieties or seedlings.

The Chinese chestnut appears at this time to offer the greatest opportunity for improvement by breeding. The trees do not attain the large size of the American species, which is undesirable, but they do become somewhat larger than the Japanese, which in this country seldom exceed the apple tree in size. The Chinese chestnut is highly resistant to blight, and so far as observed the best seedlings and varieties bear freely without being overproductive. Some of the heaviest- bearing trees of this species in a seedling orchard located at the United Station Pecan Field Station, Albany, Ga., now 10 or 12 years of age, are annually producing from 50 to 70 pounds of nuts each. The finest nuts of the Chinese species are about all that could be desired. The largest are equal in size to the average chestnuts imported from Italy as commonly seen in eastern cities from midfall until after the holidays. Typically the Chinese chestnuts are of dark, chocolate-brown. color, overlain with thick to thin gray or whitish down that may cover the greater part of the exposed surface er be confined to a small area immediately surrounding the apex. They are commonly glossy and attractive. Some are only mildly sweet, but others are excellent.

With regard to automatic separation of nuts from the burs, as well as time of maturity of crop, marked variability exists among seedlings and varieties of all species. As a rule the Chinese and Japanese chestnuts ripen earlier and separate themselves from the burs better than either European or American chestnuts.

PRESENT BREEDING WORK

Breeding work is largely confined to the Chinese chestnuts, though the Japanese may be useful to some extent. The present work in improving the Chinese chestnut necessarily involves the selection of seedlings promising as new varieties and the use of such varieties in actual breeding by hybridization. During the past several years the United States Department of Agriculture, Bureau of Plant Industry, through its Divisions of Fruit and Vegetable Crops and Diseases and of Forest Pathology, has examined nuts from several hundred trees in various parts of the country. Probably 100 seedlings are now under observation. Scions of many of the best have been grafted upon nursery stocks and are now on their way to early bearing. Three of the trees tentatively selected in 1930 have been propagated by individuals outside the Department and to some extent are being commercialized, although they are by no means fully tested or approved by the Bureau. One of these is known as Carr, after R. D. Carr, Magnolia, N. C., to whom the original tree was sent by the Bureau in 1919. Another is Hobson, so called after James Hobson, Jasper, Ga., to whom, with a number of others, it was sent in 1919. The third variety is Zimmerman. This was selected by the Bureau from a lot of seedlings grown by G. A. Zimmerman from nuts imported by him in 1924 through Nanking University, Nanking, China.

The trees under observation also include a number of Japanese seedlings that now appear to be of considerable promise. The majority of these are of recent origin, as they were brought to light in 1929 as a result of cash prizes financed that year by John Harvey Kellogg, Battle Creek, Mich., through the Northern Nut Growers’ Association.

The aims in breeding are to produce varieties that will be of value for the general market or the home or both. The desired characteristics at present are resistance to blight and: weevils, heavy annual bearing, moderate precocity, early and quick maturity of nuts ahead of frosts, automatic separation of the nut from the burs, not more than three nuts to the bur, large but not of too great size, attractive appearance, freedom from shell splitting, thinness of pellicle, automatic separation of kernel from pellicle, fine texture, good flavor, and good keeping quality. Hardiness in all parts of the native or adapted range of the chestnut is also important.

In the appendix will be found a list of persons now engaged in the improvement of the chestnut through breeding.

FILBERT

The term "filbert" is used in this article in accordance with the popular American usage and is understood to imply a superior type of nut of the botanical genus Corylus. The term “hazel” is used for the inferior and smaller nuts. In Europe the distinction is drawn upon the basis of length of husk in proportion to that of the nuts. Those that have husks no longer than the nuts are called hazels, while those with husks longer than the nuts are called filberts. This distinction is difficult to follow, once the husks have been removed.

At least four species of Corylus are under cultivation for nut production. Two of these are tree forms attaining a height of 80 to 125 feet. Both are commonly called hazels, as the nuts they bear are rather small, thick-shelled, and inferior in edibility. One is the Turkish or Constantinople hazel, C. colurna L., of southeastern Europe and western Asia. According to Rehder (28), this species was introduced in 1853. It is extremely hardy, doing well in western New York, where three fine trees 50 feet tall are to be seen in Highland Park, Rochester. It is used in this country for ornamental planting and as a stock on which to graft superior varieties of the European filbert. The latter use is still in the experimental stage and is not recommended for commercial purposes. The other tree species is the Chinese hazel, C. chinensis Franch., which Rehder states was introduced into this country in 1895. Its usefulness for stock or other purposes has not yet been determined.

Two native species of Corylus that are being used to some slight extent in the development of varieties are the eastern hazel, C. americana Marsh., and the beaked hazel, C. cornuta Marsh. Both are shrubby species producing nuts ordinarily of little value. The former has much the greater range in this country, as it is common from the Lakes to the Gulf, whereas the latter occurs only in the northernmost States. Nuts of the eastern hazel have husks longer than the nuts, and they develop as overlapping valves opening at one or both sides to the base. The beaked hazel has long, tubular, and thickly spiny husks, which remain tightly closed. A form found on the Pacific coast, greatly resembling the latter and known by some authorities as C. californica Rose, but by others as a form of C. cornuta, is common as a wild shrub from California north to Washington. This has been used little or not at all in breeding work. A number of varieties of C. americana have been introduced into garden culture in the East and are being grown by nurserymen. The three best known are Rush from Pennsylvania, Littlepage from Indiana, and Winkler from Iowa. Rush has been used extensively in breeding new hybrid varieties. Littlepage and Winkler have been used to some extent in this way.

The commercial production of filberts is now an important industry in the Pacific Northwest, especially in the Willamette Valley of Oregon and in nearby parts of western Washington. Most. of the varieties are of the species Corylus avellana L., although some are of C. maxima Mill. and others are apparently hybrids between these two species. Trees of the former often attain heights of 25 to 30 feet, and many of those first planted in this country now have trunks fully 18 inches in diameter a foot or so above ground. Those of the latter are said to attain a height of 30 to 35 feet in Europe and Asia, but no trees of such size are known in this country. The husks may be shorter or longer than the nuts, or of the same length. All cultivated varieties except those of C. maxima parentage have husks that are open or overlapping at the sides. The husks of C. maxima varieties remain tightly closed. The nuts may or may not be naturally discharged free from the husks; varieties of C. avellana vary greatly in this respect. Typical varieties of C. avellana_are Barcelona, Bolwyller, Du Chilly, Daviana, and Italian Red. White Aveline is the best known variety of C. maxima parentage.

NEED FOR CROSS-POLLINATION

As far as known all varieties of Corylus are self-sterile and must be interplanted in order to assure effective pollination, a fact that is of rather recent discovery, although it became known more than a century ago that varieties are often made more fruitful by the application of additional pollen from other trees to the pistillate flowers of those having a scarcity of staminate flowers. This appears to have been the discovery of George Swayne of England about 1821.  He discussed it at some length in a paper On the Fertilization of the Female Blossoms of Filberts, which he read February 18, 1823. The paper was published the following year in the Transactions of the Horticultural Society of London.

In that paper Swayne told of a series of experiments begun by him in 1820 and continued for 3 years. During the first year he suspended catkins of the wild hazel (Corylus avellana) in the tops of two filbert trees having profuse pistillate blooms but a scarcity of staminate flowers. The trees had been owned by him for 14 years, during which time there had been practically no crops. That year, however, following the application of abundant pollen, the yield was “exactly 2 pounds.” With this encouragement he checked the experiment the following year by first noting as before that the pistillate flowers were abundant but that there were practically no staminate flowers. He refrained from adding pollen and the crop that year was again a practical failure. The next year, when for the third time there were many pistillate flowers and few staminates, he made applications of pollen from the wild hazels to the stigmas of the garden trees. The crop was again very good, and soon after the harvest he reported the results of his 3 years’ work.


Figure 1.—John Franklin Jones (1871-1928), Lancaster, Pa., introducer of many valuable varieties of nuts. He is believed to have been first to breed filberts by hybridization of species. Beginning in 1917, he sought to cross European varieties of Corylus avellana with the Rush hazel, C. americana. Being entirely unsuccessful for 2 years, he reversed the order in 1919 with immediately favorable results. By this method he developed the Bixby and Buchanan varieties, which have been named and introduced since his death.

So far as known, the next investigation of this nature occurred almost a century later when, in 1917, the late J. F. Jones (fig. 1), of Lancaster, Pa., sought to hybridize the European varieties of filbert with the Rush variety of American hazel, Corylus americana (fig. 2, A). He and many others had found the former not commercially hardy in the East, and the Rush was the best of the native hazels that came to his attention. For 2 years he applied Rush pollen to the pistillate flowers of several European varieties, with negative results. In 1919 Jones reversed the order and there was a good crop of nuts. These were planted during the following spring, and from that time until his death in January 1928, Jones was an active and enthusiastic filbert breeder. His hybrids came into bearing early, and by 1924 about 100 were in fruit. By the end of the next 3 years he had selected 12 to 15 for further observation and eliminated a considerable number. One that had been numbered 200 proved so promising that he was seriously considering its propagation and introduction to the public. This plant was the result of a cross between Rush and Italian Red. It has since been named Bixby (fig. 2, C) after the late Willard G. Bixby, of Baldwin, N. Y., a friend and coworker of Jones. Another plant, no. 92, greatly resembling Bixby, but shown by Jones’ record to be a Rush X Barcelona cross, has been named Buchanan (fig. 2, C) and is being propagated for the nursery trade.  Both Bixby and Buchanan are apparently of considerable promise for home planting in the East.


Figure 2. Corylus varieties that have been successfully used in eastern filbert breeding:
A. Rush (C. americana), the pistillate parent mainly used;
B. Barcelona (C. avellana);
C. Rush X Barcelona, Buchanan variety;
D. Du Chilly (C. avellana);
E. Rush X Du Chilly;
F. Italian Red (C. avellana);
G. Rush X Italian Red, Bixby variety;
H. White Aveline (C. maxima);
I. Rush X White Aveline

EUROPEAN FILBERTS IN THE EASTERN UNITED STATES

In the aggregate there has been a large amount of selection work with the filbert in this country during the past century or more. Plantings of European varieties and seedlings have been made frequently in various sections.  Most of the better varieties and seedlings were introductions made during the eighties and nineties by the late Felix Gillet (fig. 3), a Frenchman who established a nursery at Nevada City, Calif., in 1871. A good many introductions have been made by others, so that altogether several hundred varieties and seedlings from Europe have been tried out in this country. The best of these have proved commercially profitable only in the Pacific Northwest. They have been successful in the East to a limited degree and as a rule only when grown in situations well protected from extremes of temperature, as by a large body of water, a building, a hill, or a group of trees.


Figure 3.—Felix Gillet (1835-1908), proprietor of Barren Hill Nurseries, which he established at Nevada City, Calif, in 1871. He was one of the most outstanding figures of his time in introducing carefully selected varieties of filbert, Persian walnut, and chestnut from Europe.

Three known factors stand in the way of success with the European varieties of filbert in the East. The most important is a serious blight, Cryptosporella anomala (Pk.) Sacc., which causes little injury to the native species but spreads quickly and with fatal results to European varieties planted in the vicinity. The likelihood of serious losses by this disease has decreased greatly during the last half century with the more or less general eradication of the native hazel plants on roadsides and fence rows, incident to clearing the land. However, the disease is still a grave menace whenever either European varieties or the new hybrids (Corylus americana X avellana) are planted near native species growing wild.

The second factor is lack of hardiness. Most European varieties of filberts are subject to winter injury, which may kill only the staminate flowers, or the pistillate ones, or both, or it may kill the tree tops, or even the tree trunks to the ground. As a rule, however, only the flowering parts are injured.

The third factor is self-sterility.  So far as known all varieties are largely, if not entirely, dependent upon other varieties for effective pollination. Until recent years most plantings in the East were made without regard to pollination requirements.

Some of the men who were most active in the introduction and early testing of varieties of filberts in the Pacific Northwest were A. A. Quarnberg (fig. 4), Vancouver, Wash.; Thomas Prince, Dundee, Oreg.; and George A. Dorris, Springfield, Oreg. Among those most recently active in the field of selecting and testing new varieties are Pearcy Bros., Salem, Oreg.; H. A. Henneman, Portland, Oreg.; A. M. Gray, Milwaukie, Oreg.; W. A. Schmidt, Corvallis, Oreg.; A. B. Scherf, Newberg, Oreg.; and D. Fitzgerald, Washougal, Wash. These men procured their trees mainly from Gillet, but to some extent they made direct importations. Among those in the East who have contributed most to filbert culture since the early eighties may be mentioned the United States Department of Agriculture; the New York State Agricultural Experiment Station at Geneva; A. S. Fuller, Ridgewood, N.J.; J.W. Kerr, Denton, Md.; Conrad Vollertsen, Rochester, N. Y.; Robert T. Morris, Stamford, Conn.; W. G. Bixby, Baldwin, N. Y.; and J. F. Jones, Lancaster, Pa. Vollertsen brought a number of varieties from Germany in 1912. Of these, Italian Red (fig. 2, F) is the only one now in special favor among eastern planters. Dr. Morris introduced a valuable seedling from Bohemia, which he later named Bonybush. The other men named in this group made their contributions by testing varieties in their respective localities.


Figure 4.—A, A. Quarnberg (1849-1933), Vancouver, Wash., one of the leading figures in laying the foundation of both the filbert and Persian walnut industries in the Pacific Northwest. He was one of the first to plant and test most of the varieties now of leading importance in that part of the country.
RAW MATERIAL FILBERT BREEDING

Most filbert varieties of either American or European production are without conspicuous merit. As previously noted, few are both hardy and fruitful except in specially favorable environment. Most filberts are of medium palatability and the nuts of many varieties are often imperfectly developed and the kernels thickly coated with coarse fiber. Some varieties are poor bearers, or the nuts may be too small or too thick-shelled to be acceptable on the market. Many are difficult to extract from the husks, and some produce only small quantities of pollen.

Some varieties are very good in quality and flavor. The nuts of some are of good size and thin-shelled. . The kernels are often plump and bright-colored. The best nuts are entirely free from coarse covering over the kernel. However, some of the finest are too small for commercial use. White Aveline (fig. 2, H) is typical of the mixture of good and bad characteristics found in filberts. In quality of kernel it is one of the finest varieties known. It also has a remarkably thin shell; but, since it belongs to the species Corylus maxima, it has a long, tubular, tightly closed husk, which fails to open at maturity, and husking is difficult.

The variety with the greatest number of good points now grown in this country is Barcelona (fig. 2, B), which was introduced from Europe by Gillet probably during the seventies or early eighties. The tree is a vigorous grower and a good bearer; the nuts ripen early and within a short period and readily fall free of the husk. They are attractive in appearance and of large size. The shells are of medium thickness, and the kernels are usually plump, clean, quite sweet, of fine texture, and fairly rich. The nuts are roundish in form, although variably so. The kernels are not so clean or free from covering over the pellicle as some others, nor are they the best in flavor. Nevertheless, everything considered, commercial growers of the Willamette Valley, Oreg., have thus far found this to be their most profitable sort.

The second leading variety in the Pacific Northwest is Du Chilly (fig. 2, D), also an early European introduction made by Gillet. As compared with Barcelona it is moderately vigorous, not as productive, and less hardy. The nuts do not mature quite so early, and only a small proportion are naturally separated from the husks, although they are not difficult to husk. The nuts are oblong and flattened instead of being roundish. The shell is about as thick as that of Barcelona. The kernel is similar-in plumpness and about equally free from fibrous covering. It is slightly sweeter and more palatable than Barcelona. Du Chilly nuts bring a somewhat higher price in the market, which largely, if not entirely, offsets the lighter fruiting of the variety. Both Du Chilly and Barcelona are less inclined to throw up suckers persistently about the base of the tree than are some others.

Daviana is the best known of the large varieties from Europe, which are notably thin-shelled. It is an excellent pollinizer for other varieties, but is itself a shy bearer, is very subject to injury by a bud mite, and frequently the kernels are not plump. From the standpoint of the breeder, its chief advantages are believed to be thinness of shell and its value as a pollinizer.

NATURE OF THE PROBLEMS INVOLVED

The problems involved in filbert breeding are relatively simple as compared with those of the chestnut, since there is already ample material. The area in the Pacific Northwest within which commercial filbert growing is centered is relatively small and has many full collections of varieties. In the East species and varieties now thought essential are represented in collections of the Bureau of Plant Industry, United States Department of Agriculture, near Washington, D. C., and of the New York State Agricultural Experiment Station at Geneva. Breeding by hybridization has made much headway at each place. Also a valuable collection of first-generation hybrids between Rush, one of the best-known native varieties of Corylus americana, and certain leading European sorts, mainly of C. avellana, is under observation at the J. F. Jones Nurseries, Lancaster, Pa.

PRESENT BREEDING WORK AND FUTURE POSSIBILITIES

The most promising line of attack for the breeder in the East seems to be a continuation and expansion of breeding by hybridization, such as is already under way, rather than by, making further selections from European varieties or the native species, both of which generally fall below the standards of American growers or consumers. Until superior hardy varieties can be developed, the best of the American varieties are likely to be used to a limited extent for home planting in zones beyond the climatic limits of safety for hybrids or European varieties.

In the Pacific Northwest the problem of the breeder is to develop more perfect varieties, chiefly from seedlings of Corylus avellana. The problem of hardiness is less acute than in the East. A desirable variety in the Northwest would be one that is resistant to fungus diseases and insect pests, a strong grower, either self-fertile, or a good pollinizer for other varieties, and a heavy annual bearer of choice nuts. The nuts should mature early and all at one time; they should separate naturally from the husks; they should be bright-colored, uniform in size, and probably oblong rather than rounded for greater appeal to the consumer. The shells should be thin enough to be broken easily, and the kernels should be plump, clean, bright, sweet, and of fine texture. In the appendix will be found a list of breeders engaged in work with the filbert, and of varieties considered promising for breeding work.

On the western coast filbert breeding is still largely carried on by mass selection. Out of the thousands of seedlings that are being grown and tested by private growers, the best finally come under critical observation when all but an extremely small percentage are rejected. Few varieties have yet come to light that meet the dual requirement of commercial crop production and pollination of other varieties. When breeding reaches the point of seeking greater hardiness in order to widen the western range of successful production, it is not improbable that the wild species, Corylus californica, of that region will be given a trial as one of the parents, in the same way that C. americana has been used successfully in the East. Thus far, pollen of neither of these native species has been found to function on the pistillate flowers of European varieties, but as the eastern species has been useful as a pistillate parent, the same may prove true with the western one.

Filbert breeding, both by selection and by hybridization, is in progress at a number of points in the East. The United States Bureau of Plant Industry has made important contributions in its studies of varietal values not only in that part of the country but also in the Pacific Northwest. It has also made a number of important introductions of varieties from Europe. It is continuing its studies of the merit of European varieties both at the Arlington Experiment Farm, Arlington, Va., and at the United States Horticultural Station, Beltsville, Md. The work at the latter place is now largely confined to testing first-generation hybrids resulting from crosses made by its staff on the grounds of the late W. G. Bixby, Baldwin, N.Y. The pistillate parents used in making these crosses were Rush, Littlepage, and Winkler varieties of Corylus americana as well as a number of varieties of C. avellana and C. maxima. Among others used as pollen parents were C. colurna, the Turkish tree hazel, and C. heterophylla Fisch., from eastern Asia, sometimes called the "various-leaved hazel." Altogether, there are now at the Beltsville station about 2,000 hybrid plants of bearing age, transplanted from the nursery from 1932 to 1936. Several of those that have fruited appear highly promising for home use. Nuts of the first generation are a little small for sale in the unshelled condition.

Hybridization of filberts at the New York (State) Agricultural Experiment Station was begun in 1930. In 1933, 535 hybrid plants resulting from crosses made by Federal workers were transferred to Geneva from the Bixby grounds at Baldwin, N. Y. Some of these now in bearing are exceedingly promising. In addition to these plants there are 352 other plants at Geneva resulting from more recent crosses made by station workers. Climatic conditions at Geneva seem to be more favorable for varieties of Corylus avellana than at either of the Federal stations, but partial or complete crop failures are not infrequent even there.

The Virginia Agricultural Experiment Station at Blacksburg began selective breeding from Kentish Cob seedlings in 1921. The purpose has been to develop hardy varieties of merit for use in that State. One seedling has been selected as worthy of further observation.

The Minnesota Agricultural Experiment Station at University Farm, St. Paul, is breeding by selection from native plants of Corylus americana for the purpose of developing hardy varieties of value in that State for home planting. About 200 plants have been brought to fruiting and discarded. Nine hundred more are now under observation, of which some appear to have considerable promise.

Working privately, S. H. Graham, Ithaca, N. Y., is doing considerable filbert breeding, mainly by selection. However, he has brought into fruit a number of second-generation hybrids of the crosses made by the late J. F. Jones, Lancaster, Pa. From these he has made one or two selections of considerable promise.

E. M. Ten Eyck, South Plainfield, N. J., has had for many years a number of Corylus avellana seedlings grown from nuts bought on the market. These have been injured very little by winter temperatures, have borne well, and the nuts have been quite satisfactory for home use. C. P. Close and J. J. T. Graham, of the United States Department of Agriculture, have both grown for many years a considerable number of seedlings of C. avellana from which it now seems possible to make selections of value for home planting. The trees of Close are at his home in College Park, Md., and‘ those of Graham at Glenn Dale, Md.

The J. F. Jones Nursery, Lancaster, Pa., is now fruiting and continuing under test about 50 first-generation hybrids from crosses made by Jones. As already noted, two of these have been given variety names and are being propagated commercially. While it is improbable that further selections will be made for production varieties, it is possible that some of this collection will be found useful as pollinizers.

There is a large 24-year-old Barcelona tree on the premises of C. A. Reed, Takoma Park, Md., which bore a full crop for the first time in 1936, although it has bloomed freely with great regularity. Apparently it was effectively pollinated in the spring of 1936 by pollen from first-generation Rush X Barcelona hybrids nearby. If further investigation should prove that a Rush < Barcelona hybrid will effectively pollinate Barcelona, which is both self-sterile and sterile to Rush and to all other varieties of Corylus americana, the result will be extremely interesting as well as significant. If such hybrids can be used as pollinizers for Barcelona and other European varieties whose staminate flowers are easily killed by winter temperatures, the successful cultural range of such varieties might be considerably widened.

Progress already made in the improvement of filbert varieties by hybridization indicates great future possibilities for this kind of work. It should be possible within a reasonable period to develop superior varieties for commercial growing in the Pacific Northwest with which to meet the requirements of American markets now largely supplied by imports. Eastern varieties of high merit should be developed for home planting over much of the region from lower New England and the Great Lakes on the north to perhaps the Potomac and Arkansas Rivers on the south. No doubt much of Wisconsin, southern Minnesota, South Dakota, and Nebraska might also be included.

THE HICKORY GROUP

[NOTE: The genus "Hicoria" has been changed to "Carya" and the scientific name of pecans changed from "Hicoria pecan" to "Carya illinoensis". Job security for botanists. -ASC]

The hickories form an important group of trees valuable for the production of both nuts and timber. With the exception of a single species, Hicoria cathayensis Sarg., from southeastern China, the entire genus is strictly American. The hickory range extends from the Provinces of Quebec and Ontario in Canada across the eastern and central United States into northern Mexico. Fifteen species are described by Sargent in. the Manual of the Trees of North America. Of these only three or four produce nuts of particular value, although the nuts of certain others are edible in varying degrees.

From the standpoint of value of nuts the pecan, Hicoria pecan (Marsh.) Britton, is the most important member of the group. In crop value it rivals the Persian (English) walnut of the western coast. The tree is one of the largest east of the Rocky Mountains. Broadly speaking, the natural and cultivated range of the pecan covers the Cotton Belt and lower elevations northward in the Mississippi Valley into Indiana, Illinois, Iowa, and southeastern Kansas.

The pecan tree.is valuable in ornamental planting wherever climatic and soil conditions are favorable. It sometimes succeeds as far north as Connecticut, but nut production is unimportant north of the District of Columbia or the latitude of Terre Haute, Ind.

Other hickories offering inducement to breeders include the shagbark, Hicoria ovata (Mill.) Britton, the shellbark, H. laciniosa (Michx. f.) Sarg., and a number of other species of less importance, as well as various hybrid forms that occur with considerable frequency in nature. The shagbark is much the most valuable nut producer. Nuts of the shellbark, while large and alluring, are often poorly filled.

Breeding to improve hickories of any species has thus far largely been confined to selective methods. By such means a very considerable number of varieties of both pecan and others have been brought to light. Breeding by hybridization has been under way with the pecan for many years, but so far without the introduction of many varieties. This form of breeding has not yet been undertaken in earnest with other hickories.

PECAN

According to dates given by Taylor (38), pecan selection is known to have begun as early as 1846 or 1847, when scions of a variety later named Centennial were successfully grafted by a Louisiana slave named Antoine. The next variety known to have been grafted was Van Deman, in 1877, although it was not permanently named until 15 years later. The Rome variety was first propagated in 1882, Hollis in 1884, Frotscher in 1885, Stuart in 1886, and Pabst in 1890. The first pecan nursery was that of William Nelson, New Orleans, La., who began selling seedlings in 1874 and grafted trees in 1879. The period of greatest activity in the introduction of new varieties was probably between 1905 and 1925. During that time practically every important pecan center of the entire South introduced its favorite varieties of local origin.

The first carlot shipment of pecan nuts of named varieties, carefully graded according to definite standards of size and quality, is believed to have been made in 1917 by J. M. Patterson, president of the Georgia Papershell Pecan Growers’ Association, Putney, Ga. By 1920 there was a great multitude of varieties in bearing, and nuts of the same size and general character, whether from seedling trees or named varieties, brought about the same price. This caused the selling agencies to begin marketing a large portion of the crop by brand instead of by variety as had been done until that time. Now, with the exception of a few varieties, such as Schley and Stuart, most of the pecan crop, no matter whether from cultivated or wild trees, is graded according to size, form, appearance, and to some extent thinness of shell and general merit. High uniformity, possible only when varieties are sold separately, has largely disappeared, at least for the time being.

The loss of varietal status, insofar as selling pecans is concerned, has been partially due to the failure of a good many varieties to meet the requirements of successful production and marketing, and of any varieties to become outstanding. Light bearing, uncertain filling, variability in size of nuts from year to year, even from the same trees, together with susceptibility to insect pests and fungus diseases, have had much to do with a situation that has practically compelled the blending of the nuts of the different varieties together instead of selling them separately. A process of readjustment is now, taking; place throughout the entire field of production and will probably continue until a majority of present varieties have been superseded by new kinds better suited to the requirements of the orchard and the market. Future plantings will doubtless be established with superior varieties now unknown, and with greater consideration of environmental and cultural requirements.

Past Breeding Work With Pecans

Apparently the first breeder of pecans by hybridization was Forkert (13), of Ocean Springs, Miss., who began this work in 1903. He was followed 1 year later by Risien (29), of San Saba, Tex. Both men were of foreign birth, Forkert having been born in Germany and Risien in England. They spent much time in searching for the best varieties obtainable by selection from seedlings before undertaking the work of hybridization. Forkert found no chance seedlings that he thought worthy of introduction, but Risien introduced several varieties selected from wild seedlings.


Figure 5.—E. E. Risien, San Saba, Tex., a pioneer in propagation and varietal improvement of the pecan by selection and hybridization. A majority of the most popular varieties of Texas are among his productions.

Forkert’s first introduction, Dependable, was the result of a Jewett X Success cross. This proved disappointing and has since been practically abandoned. Admirable, a Russell X Success hybrid, also was a disappointment insofar as being an improvement over existing varieties was concerned. His one apparently meritorious introduction is Desirable, a variety of unknown parentage. It was not widely disseminated previous to his death in 1928, and would doubtless have been lost had it not been for scions that he sent to the United States Pecan Field Station near Albany, Ga., in 1925. From this stock the variety has been widely disseminated for test planting.

The work of Risien (fig. 5) was in a semiarid region at high altitude in western Texas. He seems to have been the first in the South to conduct a systematic survey of wild pecans for seedlings worthy of propagation as new varieties. About 1882 (30) he discovered the parent tree of the variety that he later named San Saba. He was probably the first to plant nuts from a selected tree in orchard form for the purpose of growing seedlings from which to make selections. A great many persons planted seedling trees for nut production during that early period because grafted trees were unavailable, and from such trees many good selections were made later. Risien planted chiefly for the purpose of originating valuable varieties, and in this he was successful.

Risien independently mastered the art of propagating pecan trees during the early nineties, and while he was a half century behind Antoine in this work, so far as is known he was the first propagator in Texas, and so far as he knew he was the pioneer in the field. He was the first in the South to top-work large pecan trees. In addition to San Saba, he introduced Attwater, Kincaid, and Sloan as selections from wild seedlings. Among the selections from his orchard of 1,000 San Saba seedlings are Colorado, Jersey, Libertybond, Onliwon, San Saba Improved, Sovereign (Texas Prolific), Squirrels Delight, Supreme, and Western (Western Schley). Among varieties from definite crosses are Banquet (Sovereign X Attwater), Commonwealth (Longfellow X Sovereign), Kincaid Improved (Onliwon X Kincaid), Sloan Improved (San Saba X Sloan), and Venus (San Saba X Attwater). A recent introduction is Garner (John Garner), an open-pollinated seedling of San Saba Improved.

   Another Texan who has contributed much to the pecan industry, not only in his native State but also in the entire South, is J. H. Burkett, of Clyde, Tex., for many years chief of the division of edible nuts in the State department of agriculture at Austin, and author of several bulletins on pecan culture. Burkett was the discoverer and introducer of the valuable Burkett variety, which has a large, round nut with very thin shell and excellent kernel characteristics. It has long been a favorite among planters from western Texas to the Pacific coast. It has several features that should make it desirable for use in breeding work.

   Other planters in many States, covering practically the entire South, established seedling pecan orchards having from a few hundred up to several thousand trees. One such orchard, planted in 1897 by James (17), of Mound, La., later became the source of such important varieties as Carman, James, and Moneymaker. During approximately 30 years, beginning in 1880, seedling orchards and dooryard trees on the Gulf coast of Mississippi, especially in the vicinity of Ocean Springs and Pascagoula, became fruitful sources of new varieties. It was then that Alley, Delmas, Pabst, Russell, Schley, Stuart, Success, and many others less prominent were introduced from that section. Among persons most active in the introduction of these varieties were Theodore Bechtel, C. E. Pabst, and W. R. Stuart, of Ocean Springs, and A. G. Delmas, I. P. Delmas, and F. H. Lewis, of Pascagoula.

In northwestern Florida during the nineties, seedlings grown from nuts of trees owned by Arthur Brown, Bagdad, Fla., had an important part in giving rise to varieties in that region. An orchard planted with such stock in 1886 by J. B. Curtis at Orange Heights, Fla., became the source of the Curtis variety in 1896, and of Hume, Kennedy, and Randall somewhat later. Many other Florida varieties, less well known, are believed also to have originated as seedlings of the Arthur Brown stock.

Probably the first large-scale breeding of pecans by hybridization was begun by the United States Bureau of Plant Industry in 1915 in the orchard of C. E. Pabst, Ocean Springs, Miss. Hundreds of crosses were made that year and the next, and the resulting nuts were planted on the grounds of Pabst. However, with the entrance of the United States into the World War the work was discontinued and the young trees were neglected. Pabst died in 1919, and with the change in ownership of the property the entire lot was lost.

This work was resumed in 1920 in the orchard of B. W. Stone, Thomasville, Ga., and continued for several years. The first nuts were planted on the grounds of the Georgia Experiment Station, Experiment, Ga. Of these, a Schley x Moneymaker hybrid is now believed to have considerable promise. In 1922 the United States Pecan Field Station at Philema, Ga., was established, and several thousand young hybrid trees were soon developed. In 1930 the youngest trees were transferred to the United States Pecan Field Station at Robson, La. A considerable number of trees at the former station have been in bearing for several years and are now being observed closely with regard to bearing habits, disease resistance, and merits of nuts. Some of these hybrids are highly promising but require considerable further observation.

In the North, where the native pecans are mostly small and difficult to crack but otherwise much like those of the Southeast, the first recorded steps toward selecting varieties began during the early nineties, when the Department of Agriculture received nuts from Illinois, selected mainly because of their superior size. One of the first trees to attract attention in this way belonged to H. G. Hodge, York, Ill. During the next few years this variety came to be known as Hodge’s Favorite or Illinois Mammoth, and many nuts from the original tree were sold for seed purposes. It was accorded varietal recognition by Taylor (38) in 1908, who called it Hodge.

The second northern pecan variety to be recognized appears to have been Major, discovered by W. N. Roper, Petersburg, Va., about 1907. His attention was attracted to the superiority of certain nuts in a mixed shipment that he procured for seed purposes from a merchant in southern Indiana. By persistent efforts Roper traced the nuts to the parent tree near Green River in northern Kentucky, some 15 miles southeast of Evansville, Ind.

The next step toward bringing out new northern varieties seems to have been made in 1908, when a pecan contest was held at Mount Vernon, Ind., under the direction of the Purdue University Agricultural Experiment Station. It was then that Warrick, now practically obsolete, was brought to light.

During the period of 1910 to 1915, Simpson Bros., Mason J. Niblack, and W. C. Reed, Vincennes, Ind.; J. F. Wilkinson, Rockport, Ind.; and Thomas P. Littlepage, a native of the Rockport region but then a resident of Washington, D. C., spent much time, labor, and money in searching for other worthy varieties. It was during this period that Busseron, Butterick, Greenriver, Indiana, Kentucky, and Posey were recognized and introduced. From then until quite recent years very few other northern sorts have come to notice. However, beginning in 1933 and continuing annually since, a pecan contest has been held in New Haven, Ill., under the direction of H. C. Neville, formerly farm adviser of Gallatin County. As a result of these contests several highly promising varieties have come to light, but they have not yet been offered by nurserymen. In 1934 a nut contest conducted by the Northern Nut Growers’ Association brought out several apparently desirable new varieties, which ought not to be lost. Present-day breeders of pecans are listed in the appendix.

Problems in Pecan Breeding

The known defects of present varieties of pecan are many, regardless of the reputation the species justly enjoys of being one of the finest of table nuts. In the orchard many varieties are seriously susceptible to attack by insect pests and diseases of various kinds. Other defects include shy bearing; late ripening; weak crotches, which split badly; wood that breaks under the weight of nuts, especially late in summer during storms; poor shelling characteristics; failure to fill well; lack of good flavor; and a tendency of the nuts to germinate before dropping from the trees, when dry summer weather is followed by wet periods late in the growing season.

Pecans reach the consumer in two forms, shelled and unshelled. The kernels are known in the trade as shelled nuts, and by far the greater portion of the crop is marketed in this form. Nuts of small and medium sizes from either the forests or orchards are sold as “halves” or “pieces." Pecan halves are used as salted and roasted nuts and in capping such products as cakes, breads, and candies. Pieces are used as an ingredient in pastry, ice cream, and confections. For capping, the smaller the halves the better, since this means a larger number per pound, Seven hundred per pound is usually the minimum required.

When the cultivated crop is of bumper proportions or offgrade for any reason, so that prices are inclined to drop, many of the nuts are diverted from the unshelled to the shelled market. Prices for cultivated varieties, once 10 to 50 times as great as for the medium to small nuts from the forest, are now only 2 to 5 times as great. The best prices now being received by growers for cultivated pecans is about one-fifth of what it was two decades or more ago when the great majority of the present varieties were discovered and introduced.

In the present economic status of the pecan industry the most profitable varieties are those that are the most productive largely without regard to other qualities. Fruitfulness, therefore, is the characteristic sought above all others, often to the exclusion of other important factors, particularly quality and flavor.

Some of the choicest pecan varieties, from the standpoint of the nuts alone, are no longer being planted because of extreme susceptibility to fungus diseases, failure to bear well, or deficiencies of kernel.  Often these weaknesses are aggravated by unfavorable environmental conditions such as severity of climate, poverty of soil, or too close planting. For these reasons it is impossible to attribute the failure of any given variety to any single factor or to any particular combination of factors. It is equally impossible at this time to predict with certainty the commercial requirements for varieties in the future.

However, it seems to be a reasonable assumption that pecans will be marketed more and more in the shelled condition, and varieties must be developed with this requirement in view. Present varieties can, in many cases, be made to give more satisfactory results by improving cultural practices according to knowledge now available.

Desirable combinations of nut characters are to be found in a good many varieties. In the nursery and orchard such points as ease of propagation, rapid growth, precocity, productiveness, and resistance to disease are all to be found, distributed variously among the different varieties but not in perfect combination in any. For example, well- grown nuts of the Schley variety have good size, handsome appearance, suitable form for shelling by hand or machine, very thin shells, good shelling quality, and superior kernel characteristics. The variety is easy to propagate, is a rapid grower, and forms a symmetrical tree. It begins bearing at a relatively early age and normally is fairly productive. However, the susceptibility of Schley to scab makes it un- desirable for commercial orchard use. Another example is Moneymaker, which is easy to propagate, a rapid grower, precocious, prolific, and early in ripening. On the other hand, the nuts are roundish in form, variable in size, not especially thin-shelled, not easy to shell by hand, and medium in quality and flavor of kernel. In appearance the nuts are only moderately attractive, and the tree is so susceptible to certain leaf diseases that it is no longer in favor with leading growers.

Three well-known eastern pecan varieties having outstanding points, which should be useful in breeding, are Curtis, Moore, and Stuart. Curtis nuts are among the best of any variety to eat out of hand. They are a little small but quite thin-shelled and easily cracked, and the kernels are very fine, being plump, rich in quality, and unusually sweet. Moore is one of the most prolific bearers and the nuts ripen with the earliest. Stuart is probably the most dependable variety in the Southeast. While it is not a heavy bearer, in most localities it performs consistently and the nuts are large, attractive in appearance, and uniform in size.

Among varieties of the western group, Burkett, Halbert, and Sovereign are well known and probably as useful for breeding purposes as any. All begin bearing at an early age and increase in productivity rapidly. The shells of Burkett and Halbert are remarkably thin. The kernels of all are plump, bright-colored, and distinctly superior to those of most other varieties.

The problem of improving pecan varieties by breeding is greatly affected by the uncertainty as to future market requirements. With few exceptions past efforts have been to develop varieties for the unshelled market. For this purpose, large size has been one of the principal assets. Two small varieties, the Candy, by Theodore Bechtel, of Ocean Springs, Miss., and the Reuss, by G. B. Reuss, of Hohen Solms, La., were introduced at about the same time many years ago for sale in the shelled trade. These nuts were unusually thin-shelled and of excellent shelling and kernel qualities. The parent trees in both cases were heavy bearers, but neither variety met with favor on the part of nurserymen or planters on account of the small size of the nuts. However, the nuts of neither were small enough to meet the present market requirement of more than 700 halves to the pound, and it is an open question as to whether either would be of particular value in breeding to develop smallness in size. Probably the only varieties that can meet this requirement are a few recently brought to attention in some of the Northern States but not yet well tested.

Growers as a class prefer not to produce pecans of small size. In fact it is doubtful whether it would be profitable for them to do so at the present time. The question is to what extent, if any, it would pay to raise pecans exclusively for the shelled market. The demand in that direction is usually well supplied with pecans from the forests or those from the cultivated orchards that might be classed as imperfect or surplus pecans. It may be that, with the exception of the peanut, which strictly speaking is not a true nut, none of the American-grown nuts can compete on a price basis in the retail market for shelled nuts with certain foreign species that are produced at much lower labor costs. It is certain, however, that very large pecans no longer sell readily to discriminating consumers. It is also true that greater portions of the crops from orchard trees are steadily finding their way into the shelled market. It would be very desirable, if possible, to determine the probable future market requirements as to size. In the absence of a basis for an accurate prediction as to what the future may bring forth in this direction, it will probably be well to follow the present trend, which is definitely toward nuts of medium size. The largest nuts from these crops can be separated out by sizing machines and sold in the increasingly more limited market willing to pay a premium for such sizes.

The best pecan varieties lack certain characteristics necessary to make them ideal. New varieties with all the features of an ideal nut are not to be expected until a planned program of breeding to accomplish certain definite ends is carried out. Such a program would involve the growing of a large number of second-generation hybrids from the best breeding stock. In this way alone will it be possible to develop material from which to select varieties resistant to disease and superior in other characteristics. Cytological analyses of varieties may be expected to yield information as to their value as breeding stock and to throw light on problems of pollen viability and sterility.

Present Breeding Work and its Aims

Pecan breeding as it has long been carried on by the Bureau of Plant Industry has for its objectives improvement along seven distinct lines. These are (1) hardiness, (2) disease resistance, (3) fruitfulness, (4) size of nut, (5) shell thinness, (6) shelling quality, and (7) kernel quality. The purpose is to develop good varieties that can be grown with profit in each of the three distinct natural pecan districts, southeastern, southwestern, and northern. The southeastern district extends from the South Atlantic seacoast west to central Texas. The southwestern district includes localities wherever the pecan succeeds from Fort Worth, Tex., west to Arizona and southern California. The northern district includes all localities suitable for pecan growing in the Mississippi Valley north of the latitude of Memphis, Tenn., and in the Coastal Plain or lower Piedmont regions in Virginia and northward.

No great amount of pecan breeding has yet been undertaken by State experiment stations. In cooperation with the Bureau of Plant Industry, the Georgia Experiment Station grew to fruiting several hundred seedling trees resulting from crosses made by Bureau workers at Thomasville, Ga. From these the station workers selected for further observation one designated as A-93, a Schley X Moneymaker hybrid. This is a strong-growing, fruitful tree producing nuts of considerable excellence.

The North Carolina Agricultural Experiment Station. began breeding pecans at Willard, N. C., in 1912. From a large number of seedlings of named varieties station workers have selected a Schley seedling, RT-6-4, as being of much promise. The New Mexico Agricultural Experiment Station at State College, N. Mex., has made one selection from seedlings of named varieties. This is designated as College No. 1. It grew from a Sovereign nut that had been open- pollinated.

A certain amount of pecan breeding has been started in two foreign countries. The Department of Agriculture of New South Wales is doing preliminary breeding at the Breeding Station, Grafton Experimental Farms, Sydney, Australia. Selective breeding is under way in Mexico under the direction of the Secretariat of Agriculture, Department of Stations and Experimental Fields, Mexico, D. F.

Three different sets of pecan varieties are required to meet environmental conditions in the respective American regions. Greater hardiness is being sought in order that varieties may be used. for planting north of the present limits and to safeguard more southern plantings against extremes of cold. Resistance to disease is one of the most vital points for the success of any variety. Many otherwise good varieties have had to be abandoned because of their susceptibility to fungus diseases. No factor is more important than that of productiveness. It makes little difference how worthy a variety may be in other respects—if it does not bear well it must be replaced sooner or later. By good nut size is meant medium rather than. large. Overlarge nuts are objectionable because of the tendency to develop imperfect kernels. Pecans that will average 60 to 70 to the pound are most desired in the unshelled market. Thinness of shell and ease of shelling are also being sought after, as without these characters pecans in the shell are unlikely to compete successfully with nuts of other kinds that can easily be shelled in the hands or that are sold only in the shelled condition. Varieties of pecan of probable value for breeding are listed in the appendix.

HICKORIES OTHER THAN PECANS

   Selections from species of hickory other than pecan have resulted in the naming of a large number of varieties. Relatively few have been propagated by nurserymen and none has been planted in commercial orchards. A considerable number have been top-worked on trees of bearing age, and a few, grown as nursery trees, have been established in small test orchards.

Improvement of the hickories by selection was strongly urged as early as 1855 in an article by S. Hale, Keene, N. H., in The Magazine of Horticulture, in March of that year. The earliest record of hickory selection appears even before that, as the "Perkiomen Shellbark" was brought to light in October 1853, when Abraham Wismer, of Perkiomen Township, Montgomery County, Pa., exhibited nuts of this seedling as "a large variety with thin shell and kernel of best quality.” There is no record that this “variety” was ever propagated by budding or grafting, and it may be assumed that it is now lost.

The next northern hickory to receive varietal recognition seems to have been the so-called Hales Papershell, a thin-shelled variety of shagbark discovered by Henry Hales, of Ridgewood, N. J., first recorded by A. S. Fuller in 1870 and first propagated by J. R. Trumpy, of Parsons & Son, nurserymen of Flushing, N. Y., about 1880. This variety was propagated to a limited extent and widely disseminated throughout the East over a period of many years. It is now practically obsolete.

The next varieties to receive recognition grew from nuts planted in 1885 by J. W. Kerr, Denton, Md. Kerr sent away for "shellbark” seed nuts, which he planted along the roadways of his farm. From the resulting trees he selected a number of seedlings to which he gave varietal names. He grafted some of these on his home grounds, but so far as known none was established elsewhere and none is now believed to be in existence.

Varietal names were used for hickories in the annual report for 1891 of H. E. Van Deman, pomologist of the United States Department of Agriculture. He described Leaming, from Rush G. Leaming, Sedalia, Mo.; Milford, from O. C. Cook, Milford, Mass.; and Shimar, from Samuel C. Moon, Morrisville, Pa.  In 1892 A. J. Coe, Meriden, Conn., offered a prize for the best hickory that might be submitted to the Connecticut Agricultural Society. The prize went to Whitney Elliot, of North Haven, Conn., for a variety named Elliot in his honor.

To Robert T. Morris (fig. 6), formerly a leading surgeon of New York, N. Y., but now retired and living at Stamford, Conn., belongs credit for beginning a movement in 1905 by which the majority of the varieties of hickory now known have been brought to notice. In that year he inaugurated a series of northern nut contests in which cash prizes were given for the best nuts from seedling trees. These contests were continued for 3 years, then dropped. They were resumed in 1911 by the Northern Nut Growers’ Association, a society founded in 1910 by W. C. Deming, then a physician of New York but now living at Litchfield, Conn. Dr. Morris was its charter president. The association has held many nut contests, the last in 1934.


Figure 6.—Robert Tuttle Morris, Stamford, Conn., who has contributed much to the published knowledge of species and varieties of native nuts in the Northeastern States. In 1905, 1906, and 1907 he conducted annual contests for the best walnuts and hickories. He became charter president of the Northern Nut Growers’ Association, founded in 1910. He has written many articles and one book pertaining to various phases of nut culture, especially propagation.

During recent years other similar contests have been held. In 1926, under the guidance of J. Russell Smith, professor of economic geography, Columbia University, New York, N. Y., a contest for hickory varieties was held by the Philadelphia Society for Agriculture. A contest for northern nuts, including hickories and other species, was held in Michigan in 1929, under the guidance of the experiment station at East Lansing, and two excellent varieties of shagbark were brought out, Mann and Miller. These appear to be as promising as any yet discovered. The ownership of the parent trees has since changed hands one or more times, but both varieties have been successfully established by various persons, including G. A. Zimmerman, Harrisburg, Pa.

A similar contest for hickories was held in Ohio in 1933, and one for walnuts in the following year. New York held a general contest for nuts in 1934. The Ohio contests were sponsored jointly by the experiment station at Wooster and two members of the Northern Nut Growers’ Association, C. F. Walker, of Cleveland Heights, and Homer L. Jacobs, of Kent, Ohio. The New York contest was directed by the State Experiment Station at Geneva, Cornell University at Ithaca, and S. H. Graham, Ithaca, a prominent member of the Northern Nut Growers’ Association.

Following the discovery of the Perkiomen shellbark, previously mentioned, the shellbark seems to have received little attention until about 1915, when J. F. Jones, Lancaster, Pa., selected, named, and began propagating the Stanley shellbark from near Carthage, Ind. Other shellbarks, probably more desirable, have come to light during recent years. Along with the shagbark and the shellbark, a number of other hickories, such as mockernut, Hicoria alba (L.) Britton, and sweet pignut, H. ovalis (Wang.) Ashe, have been included in the search for varieties of merit. The mockernut is a handsome tree with dense, dark green, fragrant foliage, trunk bark without scales, and nuts having thick hulls, very hard shells, and small but sweet kernels. The sweet pignut also has handsome foliage and smooth bark. The hulls are thin, the shells moderately so, and the kernels often nearly as rich and sweet as shagbark. Neither species is as commonly associated with rich bottom lands as are the shagbark and the shellbark.

Few varieties of sweet pignut have been recognized or propagated. Probably the first and one of the very few introduced was Brackett, discovered in 1890 by G. B. Brackett, then of Denmark, Iowa. On the basis of nut characteristics alone a number of varieties of mockernut and other hickory species and types have been named, but very few of these are especially promising and in a majority of cases considerable uncertainty exists as to the identity of the reputed species.

Many natural hybrids between Hicoria species have been given varietal names and propagated to some extent. In many cases the parentage on both sides is reasonably certain, but in others it is a matter of conjecture. Some of the earliest hybrids to become known were apparently pecan X shellbark crosses, including McCallister from Indiana, Nussbaumer from Illinois, and Rockville from Missouri. The Burton variety from near Owensboro, Ky., is supposed to be a pecan X shagbark cross. All of these were first grafted during the early nineties, or possibly earlier.

The natural type of hybrid of special value occurring most frequently among the hickories is probably shagbark X shellbark, one of the best varieties of which is Weiker, discovered in Lancaster County, Pa., by J. G. Rush, of West Willow, and first propagated in 1903 by J. F. Jones, then of Monticello, Fla. Other supposed hybrids are apparently crosses between pecan and bitternut, shagbark and _bitternut, and pecan and mockernut.

Problems and Possibilities in Hickory Breeding

   Hickory nuts have never met with the popular favor accorded pecans and black walnuts. In the shell they bring too low prices to justify shipment over long distances or extensive handling. Sale in the shelled condition is largely limited to small lots in local markets. Before nuts of the slow-growing hickory species can be expected become popular enough with consumers to justify the planting of extensive orchards, irrespective of time or cost involved in bringing the trees into full bearing, varieties must be found or developed that can be shelled easily. Until this is done hickory nuts in the shell will probably continue to compete poorly with pecans, almonds, chestnuts, peanuts, and many of the Persian walnuts, most of which can shelled easily without mechanical aid. All known varieties of pure species, and with few exceptions all of the hybrids, have shells either too thick or too hard to be cracked readily in the hands, though the shells of many may be readily broken open with a light tap of a hammer or by the use of some of the hand-power devices now on the market. The shells of many varieties split open when the nuts are hit on an edge with a hammer in such way as to release one half kernel perfectly while the middle partition holds the other half practically as securely as before the nut was broken open. A few varieties of Shagbark have been found with shells of such thinness that breaking in the hands is not difficult, but in all such nuts that have been examined by the writers the cleavage has not been good. Instead of cracking along definite lines, the shells have merely mashed at the points where pressure was applied with another nut. With the exception of the pecan X hickory hybrids and pure pecans, which are usually oblong, all nuts of hickory varieties have been generally roundish in form and therefore quite unsuited for shelling in automatically fed machines.

The parent trees of some of the varieties are known to be heavy bearers during favorable years, and top-worked trees have come into bearing relatively soon, that is, in about the same time as is required for apples. The kernels of some are plump, bright-colored, sweet, and palatable. To many persons, especially to those who knew good shagbarks and shellbarks in childhood, no other nuts taste so good. However, it is too early in the growing of these hickories to know how well any of them will be received by consumers, even when prepared in convenient and attractive form.

The problem of breeding other hickories, as in the case of the pecan, is difficult because of uncertainty as to what characteristics are likely to meet market requirements best. However, it may be assumed safely that the requirements for these hickories will not be very unlike those of the pecan and other nuts that are popular in the shell. In at least one respect other hickories should have an important advantage over the pecan. With the latter, seedling nuts of good size, good form for shelling, thin shells, and general excellence are not uncommon in the wild product. If such nuts exist among other hickories they have not yet been brought to light, in spite of many searches that have been made. When superior varieties of hickory are developed by breeding, as seems well within the realm of probability, they will have no competition with nuts of the same types, either wild or imported.

A small amount of breeding of other hickories by hybridization has been undertaken by the Bureau of Plant Industry. The objectives are much the same as for pecans. However, hardiness is more important than with the pecan because there is greater demand for varieties that can be grown successfully beyond the northern limits to which the various species are naturally adapted. This demand is from home owners who at present are unable to grow nuts of any kind for family use.

Nature has already laid much of the foundation for the hybridization program with hickories. It has produced many interesting hybrid forms, of which some may have considerable horticultural value. The majority of the first-generation hybrids are of little or no value except for novelty planting or further breeding. Very few second-generation hybrid populations have been grown, and until facilities are available for growing and studying large numbers of such progenies, progress will be slow in the selection of new and valuable types.

The natural hybrids are suggestive of what may be expected from crosses between certain species. For example, thinness of shell, and to a varying degree astringency, seem to be dominant in all bitternut (Hicoria cordiformis (Wang.) Britton) hybrids, and elongation of nut seems dominant in pecan X shellbark hybrids. Also, large size and uncertain or poor filling appear to be characteristic of hybrids between the pecan and either the shagbark or the shellbark.

By systematic breeding it should be possible to extend the range of the shagbark and other good hickories both north and south of present limits. A new form having the thinness of shell, the easy shelling character, and the rich quality of the pecan, the whiteness of shell of the shagbark, and the flavor of either pecan or shagbark, would be a great benefit to the nut industry. Such a nut is needed by orchardists, small home owners, and consumers.

In the appendix are given the names of breeders interested in improvement of the hickory and a list of varieties of probable value for breeding.

WALNUTS
BLACK WALNUT

Five species of black walnut occur naturally in this country. Four of these are from the far West and Southwest and one from Texas. Of the former, two are from California, one from Arizona and New Mexico and one from New Mexico, Texas, and Oklahoma. The two California species are known as the Hinds or northern California walnut, Juglans hindsii Jepson, and the southern California walnut, J. californica S. Wats. The former grows to be a fairly large tree, now more commonly seen along roadsides and about residence grounds, where it has been planted for shade and ornamental effect, than in forests and fields. Nursery seedlings of this species are the stocks chiefly used on which to graft varieties of the Persian walnut.

The southern California walnut is a smaller growing and less valuable tree. It varies greatly in habit, depending upon its environment. Being drought-resistant, it often occurs in dry, gravelly, or unfriendly soils where other species of walnut would certainly fail entirely. Under such conditions it develops as a true shrub only 5 to 10 feet in height instead of as a standard tree. When conditions are more favorable it grows rapidly and becomes a fairly good-sized tree. It differs from the Hinds walnut in lacking a central leader, as its branches spread out in more or less vase shape. It is not planted to any great extent.

The two walnut species native in the Southwest are much alike and nowhere of great value. One is Juglans major (Torr.) Heller, from Arizona and southern New Mexico. This sometimes attains a height of 50 feet and a trunk diameter of from 3 to 4 feet, although ordinarily it is a small tree. The other species is J. rupestris Engelm., from parts of New Mexico, Texas, and Oklahoma. This is a shrubby tree rarely attaining a height of 30 feet. The nuts are the smallest of any American walnut. Generally speaking, all of these western and southwestern walnuts are of little value for either timber or nut production. They should be useful, however, in breeding hybrid strains for that part of the country.

The eastern black walnut, Juglans nigra L., is the most important native walnut of this country in both timber and nut values as well as in extent of native and adapted range. No other American timber tree equals it in value for such special uses as cabinetmaking, interior finishing, and the manufacture of many articles, particularly gunstocks. Few other tree species are so widely distributed over the entire United States. It is grown to some extent in practically every State in the Union. Under the most favorable conditions it sometimes attains a height of 100 to 150 feet and a trunk diameter of more than 6 feet. The nuts are variable in size, form, thickness of shell, and shelling quality and also in character and flavor of kernel. The kernels of this species are favorites with manufacturers of confections and baked goods on account of the extent to which the pleasing flavor is retained in the cooking processes. So far as known, the eastern species is the only black walnut thus far used in breeding.

The history of breeding the eastern black walnut closely parallels that of the northern hickories. It has been limited chiefly to the selection of varieties from wild trees, the propagation and testing of many of these by amateurs, and the commercial planting of a few. The Thomas variety from Montgomery County, Pa., discovered, named, and first propagated about 1880 by J. W. Thomas & Sons, nurserymen, of King of Prussia, Pa., appears to have been the first to attain varietal status. It has since been widely disseminated and is still the general favorite with most planters. Its seedlings are notable because of their vigor and rapid rate of growth. Six varieties, including Thomas, were described by the Department of Agriculture in a special report (16) issued in 1896. One of these was named Peanut because of the more or less cylindrical and peanutlike shape of the single-lobed kernels. So far as is known, with the exception of Thomas, no other of these varieties is now being grown.

The introduction and testing of black walnut varieties received little further attention until early in the present century. It was largely as a result of nut contests begun in 1905 by Morris, and later expanded by the Northern Nut Growers’ Association and other organizations and individuals, that this interest became somewhat general. The industry received its next major impetus about 1915 when the prize varieties were first propagated by nurserymen and made available to the public. A large number of promising varieties are now on record. Many of these have been propagated to some extent.

Following the lead of Morris in bringing out new varieties, and cooperating closely with him, mainly through the Northern Nut Growers’ Association, W. C. Deming, J. Russell Smith, Swarthmore, Pa., the late W. G. Bixby, and the late J. F. Jones conducted many surveys in the East to discover black walnut seedlings suitable for varietal recognition. The Bureau of Plant Industry has participated actively in all of these efforts.

During recent years other black walnut contests have been conducted by the State experiment stations of Michigan, Ohio, and New York, and also by a number of individuals, especially N. F. Drake, Fayetteville, Ark., and H. F. Stoke, Roanoke, Va. In most of the association contests Deming did much of the detail work and participated actively in all judging. In this he was closely followed by Bake during a period of about 15 years beginning in 1918. Smith took entire charge of advertising the 1926 contest, which was one of the most important ever held by the association. He has been one of the principal judges in several of the contests.

Of the eastern black walnut varieties that have been brought to light in various ways, several are now grown by nurserymen. The best known of these are Creitz from Indiana, Cresco from Iowa, Ohio from Ohio, Rohwer from Iowa, Sifford from Virginia, Stabler from Maryland, Stambaugh from Illinois, Tasterite from New York, Ten Eyck from New Jersey, and Thomas from Pennsylvania. Many other varieties from New York to Arkansas and from Minnesota to Virginia are also being tested, primarily by individuals, although to some extent by public institutions. Many of these merit much greater attention than they are receiving. Unless they are propagated soon, they are likely to be lost.

The Bureau of Plant Industry has made many crosses for the purpose of developing better varieties, but so far all have suffered from adverse circumstances and few nuts have been produced. A small number of hybrid trees are now growing on the grounds of the United States Horticultural Station at Beltsville, Md. The Minnesota Agricultural Experiment Station is growing many seedlings of certain northern varieties for the purpose of selecting individuals hardy and otherwise of merit in that latitude.

As with the hickories, practically no varieties of black walnut have yet been fully tested in orchard plantings. The shells of all black walnut varieties yet recognized are much too thick to be cracked except by mechanical means, although some shells are less thick than others.

BUTTERNUT

What has been said concerning the varietal status of the eastern black walnut is largely applicable to the butternut, Juglans cinerea L., although considerably less progress has been made in the development of choice varieties. This species has a rather restricted range within the Eastern States, but it occurs naturally as far west as eastern Nebraska. At present it is nowhere abundant over large areas. As a tree it does not equal the black walnut in size, although in a favorable environment it sometimes reaches 100 feet in height and nearly 4 feet in trunk diameter. The nuts are oblong, cylindrical, sharp-pointed at the apex, bluntly rounded at the base, rough and jagged over the surface, and usually thick-shelled. Nevertheless some varieties have very good shelling quality and the majority have kernels with a rich, agreeable flavor. In cooking and in the manufacture of confections the butternut shares the popular favor of the black walnut.

The first variety of butternut to be named seems to have been Aiken, discovered in 1917 by S. E. Aiken, Grasmere, N. H. It was first propagated in 1918 by J. F. Jones, Lancaster, Pa. Other varieties have since been found mainly as a result of contests held by the Northern Nut Growers’ Association, but none have been commercialized.

While most varieties of butternut have thick shells and are difficult to crack, some crack so well with hand-power machines, of which several are on the market, that the kernels are released in unbroken halves.

This species has been greatly neglected by horticulturists. Besides producing nut kernels of excellent quality the species is the hardiest member of the walnut genus, its native range extending well into Canada. It is abundantly worth development wherever it succeeds, especially in the North.

JAPANESE WALNUT

The Japanese walnut, Juglans sieboldiana Maxim., was first introduced into this country about 1860. It has since been widely tested in practically all parts of the country without anywhere attaining great importance. The tree has much the size and general form of a large apple tree. Its nuts are of two distinct shapes, and botanists at one time thought there were more than one species. One of these was called J. cordiformis Maxim., literally “heart shaped”, from the shape of the nuts. However, there is but one species, as the tree characteristics are identical, and seed nuts of either type produce offspring of both fruit types as well as of many intermediate forms.

The nuts of both types are smaller, of smoother surface, and with somewhat thinner shells than eastern black walnuts. In general, both Japanese walnut types are top-shaped and sometimes sharply pointed at the apex: Those once called Juglans cordiformis are now known as heartnuts. These are the better of the two and are now receiving the attention of horticulturists. The late J. F. Jones propagated a number of varieties, beginning in 1918 with one that he called Lancaster. Somewhat later he introduced Bates, Faust, and Ritchie. These make quick-growing trees of much ornamental value. The nuts are excellent. Often the flavor is indistinguishable from that of the best butternuts.

The Japanese walnut, the butternut, and the Persian walnut blossom about together and 2 or 3 weeks ahead of the black walnut. Consequently they hybridize freely. The stamens and pistils of individual flowers mature at different times, usually the stamens first, and this, with wind distribution of pollen, tends to promote cross- pollination. By breeding it should be possible soon to develop valuable new forms not grown elsewhere, which would therefore have no competition with others of their own kind either imported or grown in the forests of this country. The hybrids are usually very vigorous and luxuriant in foliage, but fruit setting is sometimes very meager in spite of abundant production of both staminate and pistillate blooms. Size of tree seems to have little relation to the number of nuts produced.

Seedling Japanese walnuts grown in this country often produce nuts greatly resembling butternuts. This occurs with any generation, beginning with direct importations and continuing indefinitely. With imported seed this is undoubtedly due to reversion to a parent type common in the Orient, known as the Manchurian walnut, Juglans mandshurica Maxim., which is so much like the American butternut that it is considered to be the same by most travelers from this country. In other cases the resemblance is quite definitely known to be due to hybridization with either butternut or Persian walnut. It is possible that there may be occasional crosses with the eastern black walnut, J. nigra, but no case in which this appears probable has come to the attention of the writers.

As a rule the nuts of butternut type borne by possibly hybrid

Japanese walnut trees are usually of little value owing to the thickness of the shells and poor quality of the kernels. However, two varieties of apparently hybrid origin with the butternut as a parent are being propagated to some extent. These are Helmick from Iowa and Creitz from Indiana. The former is a discovery of James K. Helmick, Columbus Junction, Iowa, and the latter was brought out by W. A. Creitz, of Cambridge City, Ind., after whom a variety of black walnut was also named.

PERSIAN (ENGLISH) WALNUT

The Persian (English) walnut, Juglans regia L., is the best-known and most widely grown nut-bearing species of the North Temperate Zone. The tree is handsome, large, and of great value wherever it succeeds, both on account of the nuts it produces and for its timber. It is native to western and central Asia. Its nuts form an important article of food and of general commerce. Production is important in California, Oregon, and to some extent in Washington in this country, in many European countries, in China, and to some extent in Chile.

The origin and early history of this walnut is concisely given by Heiges (16), who wrote:

It was known to the Greeks, who introduced it from Persia into Europe at an early day as "Persicon" or “Persian” nut and "Basilicon” or “Royal” nut. Carried from Greece to Rome, it became Juglans (name derived from Jovis and glans, an acorn, literally "Jupiter’s Acorn” or "Nut of the Gods"). From Rome it was distributed throughout continental Europe.

It reached England prior to 1562. There seems to be no clear record of the first introduction of this walnut into the United States, but occasional references and other evidence indicate that it came with the earliest settlers. Robbins and Ramaley (31) state that "In colonial days, the term English was used to distinguish this walnut from the native American black walnut and because at that time the nuts were imported via England.”

At present Persian walnut trees occur quite frequently along the Atlantic seaboard from Long Island Sound west to Rochester, N. Y., and south to Virginia. Old trees, mostly in decrepit condition, are not uncommon. What is perhaps the oldest if not the largest Persian walnut in the United States stands on what is known as the Jacob Bauder farm, 7½ miles northeast of Reading, Pa. This tree was discovered in 1922 by the late J. F. Jones and was determined by him to be 210 years old. It measured 15 feet 1 inch in circumference at 4 feet from the base and had a limb spread of 90 feet. It is supposed to have been planted by the earliest German settlers.

Under the heading “A Giant English Walnut", the American Garden for September 1888 gave an account of a number of Persian walnut trees, one of which was still standing at that time and had been part of a planting by Roger Morris, an English gentleman, who in 1758 built a spacious mansion on his estate on Manhattan Island. The supposition is that the trees may have come from the Prince Nursery, Flushing, N. Y., which was established in 1713, 45 years previous to the Morris planting.

Other definite evidence of early planting is afforded by the so-called James River Hybrid, which was cut down in 1928. It stood on Rowe Farm, opposite Brandon, near the bank of the James River in southeastern. Virginia. This was believed to have been a natural hybrid between the Persian and the eastern black walnut. Its apparent age was estimated by Bisset (9), who observed it in 1911, to have been from 150 to 200 years. As the year of Bisset’s visit was 304 years after the settlement of the first successful English colony in this country at Jamestown in 1607, it would seem probable that the Persian walnut parent was brought from Europe and established there by colonists some time during the first century of English colonization in this country.

According to Lelong (21), the Persian walnut is supposed to have been introduced into California by the Franciscan monks in 1769. He reported that the earliest planting outside of the missions was made in San Diego probably in 1843, and that a second such planting was made near Calistoga in 1848.

The first Persian walnut planting in California to lead to commercial development was made by Joseph Sexton, of Santa Barbara, from nuts presumably of Chilean origin, bought by him in San Francisco in 1867 (36). Nuts from the Sexton trees were later used for growing seedlings for extensive orchard plantings in southern California. The nuts from these are known on the market as Santa Barbara soft-shells. Hard-shell walnuts were planted in northern California at about the same time as in southern California. It remained, however, for Felix Gillet, a Frenchman, who established the Barren Hill Nurseries at Nevada City, in 1871, to arouse interest in the whole State in grafted walnut trees of soft-shell varieties. He early imported many shipments of scions and nursery trees and was the first to introduce into California practically all of the best French walnut varieties now grown in this country.

Plantings of seedling Persian walnut trees are known to have been established in Oregon during the seventies or early eighties, as occasional seedling trees estimated to be from 50 to 75 years of age are to be found in the Willamette Valley of that State. The first commercial see in in Oregon consisted of seedling trees put out in 1893 by L. T. Davis, of Dundee, Oreg.ψ This orchard was later purchased by Thomas Prince, by whom it was materially expanded and made famous for many years as the Prince Orchard. Grafted trees began to appear in the Pacific Northwest during the late nineties, when A. A. Quarnberg, of Vancouver, Wash., and others first planted trees of French varieties, which they procured from Gillet.

The practice of breeding walnut varieties by selection appears to have been inaugurated by the French. L. D. Batchelor stated in an unpublished report on walnut culture in France that some of the varieties, such as Mayette and Franquette, had been grafted for over 100 years, and that the present commercial walnut industry of France is based upon grafted walnuts.

The planting of the seedling trees by Sexton was followed b marked expansion of seedling orchards in the southern part of California until about 1900, when many individual trees began to be selected and used as new varieties. Since about 1905 practically all plantings have been of named varieties and many seedling orchards have been top-worked.

In the Eastern States for approximately 10 years, beginning about 1915, efforts were made by J. F. Jones, and others to develop Persian walnut varieties that would be hardy in that section of the country. It was assumed that hardiness would be increased by grafting varieties on stocks of the eastern black walnut, Juglans nigra. However, practically all of the varieties so developed have since become obsolete, as they proved too subject to injury by winter cold or late spring freezes. Hardiness was apparently not affected appreciably by the use of black walnut stocks.

Persian walnut breeding by cross-pollination is still in the initial stages. Much preliminary work has been done in the way of conducting studies of blossoming habits and of pollen behavior. Varieties of this species are largely dependent upon other varieties or species of walnut for pollen for the reason that their own pollen is often not available at the time it is needed. This is because the staminate or pollen-producing flowers do not function simultaneously with the pistillate or nut-producing flowers. Usually in such cases the staminate flowers mature and shed their pollen, dry up, and fall to the ground before the pistillate flowers become receptive. Occasionally, however, this order is reversed and the pollen is shed too late to function on earlier maturing stigmas. Young trees seldom produce staminate flowers until several years after the appearance of the first pistillate flowers. Wood (46) has found that varieties of this species are entirely fertile to their own pollen when it is available at the right time, and equally fertile to pollen of any other species of Juglans.

Persian walnut hybrids, resulting from natural crosses with the Hinds walnut (Juglans hindsii) of northern California, occur with great frequency in that State. In the East natural hybridization is not uncommon with the eastern black walnut (J. nigra) or with the butternut (J. cinerea) and occasionally with the Japanese walnut (J. sieboldiana). No hybrid of these types yet found has been of horticultural value, although often the trees are vigorous growers of much beauty and not infrequently of greatly increased hardiness. No doubt some of these hybrids would furnish timber of value; but the cost of developing hybrids, added to that of bringing walnut trees of any form to timber age, is entirely too great to justify consideration of hybrids for this purpose under present economic conditions. The few nuts produced by these hybrids are usually thick-shelled and contain very little kernel.

Breeding the Persian Walnut

The principal weak points in present varieties of Persian walnuts are susceptibility to bacterial blight, lack of hardiness sufficient for conditions in the Eastern and Northern States, lack of uniformity in bearing, and general lack of quality of nuts. Some varieties have considerable astringency in the pellicle of the kernels, owing to the presence of tannic acid.

Practically all varieties are susceptible to walnut blight, a serious bacterial disease affecting both nuts and twigs. This disease is now being controlled by proper spraying, but only at great expense. Lack of hardiness is a definitely limiting factor in the East, although there are occasional trees in many of the Eastern States. Trees that survive longest in this region usually have the protection of buildings, lakes, or other agencies that modify local temperature extremes. The Persian walnut is quickly responsive to warm periods in late winter or early spring and consequently is vulnerable to frost injury. When injured by frost or other mechanical agency the tree recovers slowly. Loss by freezing is a matter of universal concern in commercial walnut districts of Europe, Asia, and the United States.

Variation in annual yield largely results from environmental influences and would be difficult to overcome or reduce through breeding alone. Nevertheless, it is more serious in some varieties than in others, and development of greater fruitfulness should result in appreciable improvement.

Some varieties are more resistant to blight than others, and because of slow response to mild temperatures, some are less subject to injury by cold in winter or spring. Other superior qualities of some varieties include fruitfulness; uniformity in size of yearly crops; shells well- sealed at the ends and so firm that they do not crack while being handled, although they are easily cracked by machine or hand; very little or no astringency in the pellicle; and richness and palatability of kernel. Such varieties, each having certain good qualities, are the material from which the breeder hopes to develop new varieties having combinations of larger numbers of desirable characteristics.

The problems involved in breeding by cross-pollination are not unusually intricate. While it is possible that better varieties or better basic material for use in breeding, particularly in the matter of hardiness, might be obtained from some foreign country, this does not seem probable, as the principal walnut regions of the world have been fairly well searched. It is believed that an abundance of varieties and strains of types desirable for breeding is already within this country. As a rule French varieties are the hardiest among grafted kinds, although a few seedlings in the East, probably of German origin, may be somewhat more hardy. However, eastern-grown Persian walnuts seldom have the high quality and relative freedom from astringency of pellicle characteristic of the western nuts, such as the French and the Santa Barbara soft-shell varieties.

Persian walnut breeding has thus far been confined to selective methods for developing greater hardiness, greater resistance to blight, heavier bearing habits, and nuts of superior quality. Nuts are desired of large but not too large size, of good sealing quality, and with shells thin enough to crack readily without breaking during normal handling. The kernels must be plump, bright, smooth, free from prominent points that break off easily, rich in quality, sweet in flavor, and without tannic bitterness in any part of the pellicle.

The New York (State) Agricultural Experiment Station has made crosses between Juglans regia and J. nigra in the hope of developing walnuts of the Persian type hardy at that latitude. Similar crosses have been made by the Minnesota Station at University Farm, St. Paul. In both cases the first-generation offspring has shown increased hardiness as well as vigor, but the nuts have been of little value.

In Mexico a certain amount of breeding by selection and of variety testing is being conducted under the direction of G. Gandara, Secretariat of Agriculture, Department of Stations and Experimental Fields, Mexico, D. F.

Breeding by selection to develop superior or even more hardy varieties of Persian walnut appears to have about reached its practical limit, as the principal walnut-growing regions of the world have been more or less thoroughly surveyed and no new varieties of outstanding merit have been found in considerably more than a decade. However, an effort is now being made by P. C. Crath, of Toronto, Canada, with the financial aid of Carl Weschcke, St. Paul, Minn., to procure Juglans regia seed from certain known trees in the Carpathian Mountains of Poland, which, it is hoped, will produce seedlings hardy in northern parts of this country and Canada. Distributions of seed nuts from that source have already been made more or less generally throughout Wisconsin, Minnesota, the Dakotas, and Ontario, Canada. Reports as to the behavior of resulting seedlings are contradictory, but there is a possibility that some of the Crath introductions will prove suitable for limited use in home plantings where other trees of the same species have not been hardy.

Breeding by hybridization in the hope of developing an entirely new form of walnut, which would be distinctly unlike any existing form and therefore would have no direct competition, is now being planned by the Bureau of Plant Industry for the early future. This is to be undertaken by crossing the Persian walnut with the butternut for hardiness and flavor, and probably with the eastern black walnut for a blend of excellent flavors and possible greater timber value. Crosses will be made so as to include the best of the Japanese walnuts, as that group is more hardy than the Persian walnut and will grow farther south than the butternut. Heartnut trees do not attain the great size of the eastern black walnut, and from that standpoint they are more desirable for orchard purposes.

Hybridization of varieties strictly within the species with possible infusion of characters from some other species on the western coast should greatly improve resistance to disease, hardiness, fruitfulness, and the general quality of nut. However, plans for breeding of this sort do not appear to have been announced by any institution or individual. Nevertheless, the possibilities are so great and the field so inviting that it is hardly to be conceived that it will long remain neglected.

In the appendix are listed varieties of black walnut, butternut, Persian walnut, and Japanese walnut, likely to be of value in breeding work, and the names of plant breeders who are actively working with Juglans.

ALMOND

The almond, Amygdalus communis L., is a close relative of the peach and therefore a member of the botanical family Rosaceae. It resembles the peach in appearance of tree, foliage, and flower. It is one of the earliest orchard fruits to blossom. In this country the blooming period is from January to March, and on this account it succeeds only in regions where there is minimum danger of killing temperatures during that period. It requires a definite although short period of complete dormancy, without which it tends to become evergreen. For this reason it is unsuccessful in the mild regions of the South.

Two types of almonds are under cultivation, sweet and bitter. To the former belong the familiar almonds of commerce, common in the markets. Of these there are three types, depending upon the thickness of the shells—hard-shell, soft-shell, and paper-shell. The Jordan is a typical hard-shell variety, the Peerless a typical soft-shell, and the Nonpareil a typical paper-shell. Seedlings of both sweet and bitter almond are used as stocks upon which to bud edible varieties.

Like the Persian walnut, the almond is of Old World origin and has been known and prized for food since the earliest times. It is supposed to have originated in the Mediterranean Basin.

It is not improbable that improvement of the almond by crude Selection began quite as early as with any orchard fruit. There is evidence that grafting was practiced long before the Christian Era. The almond is easy to bud, and it is presumable that in very early times good almonds were worked on those less good and thus perpetuated.

Almond varieties have been recognized as such for a century or more in Spain, but varieties there are types rather than clons [sic]. Almonds were first introduced into the eastern United States by pioneer horticulturists, but without success. Later they were taken to California, where, during the last half century, their cultivation has become an important orchard industry. Introductions of varieties of European origin into California began before 1853.

The first varieties introduced into California proved of little permanent value and have since been gradually supplanted by others of California origin. Out of 76 varieties rated by Wood (45) as being of commercial importance in California in 1925, 60 were of California origin, 4 of uncertain origin (probably California), and 12 only were from Europe. None of the European varieties was rated as being then in favor with experienced growers or apparently of value for future use. However, the early introductions and their ill-advised planting in various parts of the State threw much light on the possibilities of almond growing in California and on environmental and cultural requirements, and furnished material for developing better varieties.


Figure 7.—A. T. Hatch (1837-1910), Suisun City, Calif., greatest contributor to the development of almond varieties in this country. During the eighties he originated the so-called “Hatch varieties” IXL, Ne Plus Ultra, and Nonpareil, which have since been the leading sorts grown in California. At that time these became his final favorites out of many of the first selections made by him from seedlings of a bitter almond tree standing near a sweet almond by which it had doubtless been pollinated.

Almond breeding by selection from seedlings grown on a large scale for the purpose appears to have long preceded similar work with any other nut grown in this country. In 1878 A. T. Hatch (fig. 7), of California, who at one time had almond plantings in 20 counties put out at Suisun City an orchard of over 2,000 seedlings grown from nuts of a supposedly seedling bitter-almond tree which stood near a tree producing sweet almonds from which its flowers were undoubtedly cross-pollinated. The purpose was to use these seedlings as stocks upon which to bud good varieties. Concerning his next move, Hatch wrote:

I found a supposedly seedling almond which had been prolific in its bearing for several years. It was small but soft-shelled, sweet, but hard to hull and therefore expensive to handle, though I thought it was better than one that did not bear good crops, so I budded the seedling trees in place in the orchard with buds from these trees (probably this tree), but not having buds sufficient for all there were, somewhere near 300 remained seedlings. The second year after planting I found upon some of these a few almonds, some of which seemed to be very fine, sweet, soft-shelled almonds, when I concluded to leave them as seedlings until they might bear fruit.

From then on he marked the trunk of each tree in such manner as to indicate the character of the nuts and size of the crop. It was from trees so marked that he made many selections, including two that he later named IXL and La Prima.

Hatch was so pleased with the general character of the nuts from these unbudded trees that he tried to induce those that he had previously budded to push out sprouts from below the buds in order that they too might bear. In this way he was able to add greatly to the total number of promising new sorts. Among those so discovered were two that he later named Ne Plus Ultra and Nonpareil. These two, together with IXL, were his final selections; and under the popular group name of “Hatch varieties” they later took rank among the most important varieties of almond grown in this country. To some extent these have been introduced into foreign countries.

The great majority of varieties now grown in California originated as chance seedlings discovered by careful observers in various parts of the State. A few were introduced from France, mostly by Gillet. Several came from Spain as the result of introductions by David Fairchild and Walter T. Swingle, of the United States Department of Agriculture. However, next to Hatch it is probable that the man who did most toward contributing valuable varieties to California was A. M. Newlands, of Colusa. Newlands planted a sack of almonds in 1883, and 3 years later chose 4 seedlings, to which he gave the names of California White, Commercial, Eureka, and Lassen (45). Of these, Eureka is one of the best small varieties in the State.

Breeding by hybridization was begun by M. N. Wood, of the United States Bureau of Plant Industry, in 1923, in cooperation with the University of California. Thousands of crosses have been made and the resulting seedlings brought to fruiting at the State Agricultural Experiment Station at Davis, Calif. A number of promising seedlings are now under observation. Two of these are being tested in many parts of the State. Nuts from one of these and from both parents are shown in figure 8.

PRESENT WORK IN ALMOND BREEDING

Few of the varieties producing the best nuts are good bearers. Some of the best bearers are unsymmetrical trees, difficult to prune. The nuts of many of those that bear well have hard shells or are of inferior flavor. The shells of some others are of such softness that they crumble badly in ordinary handling. A considerable portion of the kernels of certain varieties are gummy and objectionable. In many cases the foliage is seriously subject to red spider injury. Some varieties are difficult to “knock" from the trees; that is, to jar off when fully mature. In some varieties there are often a great many “sticktights” or nuts from which the husk separates poorly or not at all. A few of the varieties most extensively grown produce nuts too small to bring good prices. A not uncommon defect is that of forming double kernels, called "philopenas.”

If a variety of almond could be found combining all of the good points of present varieties and seedlings, little more could be desired in the way of a first-class almond. Such desirable characteristics as late blooming; full bearing; good qualities for harvesting, hulling, and shelling; a high degree of resistance to certain insects, particularly the red spider, and to a number of diseases; and general excellence of kernel, are all to be found distributed among present varieties and seedlings.

StopTheGestapo
Figure 8.—Two of the almonds used in breeding and their offspring, which is believed to be promising as a new variety: A, Pistillate parent; B, staminate parent; C, the offspring. X 24. The nut of the new variety is superior to that of either parent in being larger, brighter in color, and of thinner shell. The kernel is larger, brighter, smoother, and of finer flavor. The tree is more fruitful and so far has been highly resistant to the red spider.

The problem of the almond breeder is to combine as many as possible of these good qualities in a few varieties. This should not be difficult, as the technique of almond breeding, like that of other rosaceous fruits such as apple, peach, plum, and others, is not especially difficult to perform. Almond pollen is carried only by insects and not by wind, and pollination is therefore easily controlled. This is quite different from walnuts, hickories, chestnuts, and filberts, the pollen of which is wind-carried, produced in great abundance, and difficult.

Present work in almond breeding by the Bureau of Plant Industry is well-organized and, as already noted, is being systematically carried on in cooperation with the University of California. Nuts from crosses made by Bureau workers are planted in nursery rows at University Farm, Davis. When the seedlings are 1 year old, scions from some of the more vigorous growers are top-worked in old trees and quickly brought into bearing. Large numbers are soon eliminated and only the most promising are preserved. In 5 to 10 years after the seed is planted further selections are made, and these are tested in various almond sections of the State by top-working on established trees. The work is making very satisfactory progress, although no varieties are yet ready for general distribution.

With the possible exception of certain of the Jordan types as grown in Spain—long, hard-shelled varieties, very popular with confectioners, chiefly because of the form of the kernel—it is generally conceded that the best almonds on the world’s markets now come from California. When the good points of the California varieties are rightly combined there is abundant reason to expect that American almonds will completely dominate the markets of this country.

Breeders now engaged in work with almonds are named in the appendix, which also contains a list of almond varieties considered valuable as breeding material.

PISTACHE

The pistache, Pistacia vera L., is a small-growing, wide-spreading tree up to 30 feet in height, dioecious in habit of flowering, and producing nuts of much value. The nuts are small in size and borne in clusters that often weigh several pounds. Each nut has a thin, reddish, leathery husk, The shell of the nut is very smooth, whitish, and thin, yet of bony hardness. It tends to split open slightly upon maturity, but not to such extent as to release the kernel. The flavor is mild, the texture fine, and the color of the kernel greenish throughout. When finely ground, pistache kernels are used to give color and flavor to confections. The darker they are the better they suit the purpose. The nuts are prepared for market by salting and roasting while still in the shell.

The pistache grows in hot dry regions where it withstands adversity better than either the almond or the Persian walnut. It is Native in Syria and nearby regions. It was first introduced into the United States in 1853-54 by the Commissioner of Patents, by whom seeds were widely distributed throughout the Southwest. Little interest was aroused, however, until 1876, when other introductions were made by G. P. Rixford, of San Francisco, Calif., by whom trees were brought into fruit in 1881. Many more recent introductions have been made by the Division of Plant Exploration and Introduction, Bureau of Plant Industry.

There are now numerous small plantings of pistache trees in the interior valleys of central and southern California. For many years the most extensive grower in that State was Claude Tribble, of Elk Grove. He made many experiments in propagation, including the use of different species as stocks upon which to graft the better varieties. In his experience Pistacia atlantica Desf. proved more satisfactory than P. chinensis Bunge. Others have used P. terebinthus L. as a stock with satisfactory results.

Much work is still necessary to determine the most satisfactory pollinizers to use for the cultivated varieties. Practically no work in breeding has yet been reported and so far as known none is planned for the immediate future. However, the superior merit of this species and its ability to grow under conditions to which no other nut of this country is well adapted would seem to justify immediate attention by our breeders.

THE TUNG TREE

The tung tree, Aleurites fordii Hemsl., is the hardiest and most valuable member of a group of closely related tropical and subtropical trees producing inedible seeds or nuts from which a valuable drying oil is extracted. This oil has been used in the Orient for many centuries in waterproofing wood, paper, fabrics, and other products. Within the last half century it has come into important use in Europe and the United States in the manufacture of waterproof varnishes, paints, paint dryers, and linoleum. Tung oil is much like linseed oil but dries more rapidly and is more resistant to water. The tree is handsome, having a round top and dense, catalpa-like leaves.

The species was introduced into the United States in 1905 by the Division of Plant Exploration and Introduction through the efforts of David Fairchild, then in charge, and United States Consul General L. S. Wilcox, Hankow, China. It has since attracted wide attention among planters in northern Florida, southern Georgia, and Gulf Coast States westward to Texas.

The earliest plantings were entirely of seedlings chosen without regard to hardiness, fruitfulness, or merit of nuts produced. In 1923 studies as to relative merits of strains and seedlings were begun by the Florida Agricultural Experiment Station at Gainesville. Later, similar work was taken up by the State stations of Georgia and Louisiana and by certain individuals, notably the late J. B. Wight, Cairo, Ga. Several selections have been made, and in a few cases these have been placed on a varietal basis by budding and grafting in the nursery. One commercial orchard of grafted trees consisting of about 4 acres has been established at Cairo, Ga.

The Florida station found that seed nuts planted in early winter or midwinter often result in trees ranging from a few inches up to 6 to 8 feet in height by the end of the first season. Such large trees may be budded during the late summer or fall. The buds will remain dormant until the following spring, when the tops should be cut back and the buds made to push out. In this way budded trees suitable for transplanting may be grown in about 24 months from the time the seed is planted.

Active hybridization was begun by the Florida station at Gainesville in 1929. Several selections from the resulting seedlings have since been made, but their value has not yet been fully determined. Selective breeding at the Georgia Coastal Plain Experiment Station, Tifton, Ga., begun in 1933, has resulted in the selection of three promising seedlings, nos. 24, 39, and 49. Breeding through pure-line selection and hybridization was begun at the Louisiana Agricultural Experiment Station, Baton Rouge, in 1935. The objectives at each of the stations are much the same; that is, to produce varieties that are hardy, vigorous, and heavy producers of good nuts rich in oil.


Figure 9.—Nature of growth and blossoming habits of hickories and walnuts as illustrated by the pecan. A, Twig showing staminate flowers (a) borne axillary on growth of the past season and (b) pistillate flowers borne terminally on growth of the current season. B, Section of a catkin showing three staminate flowers of the many that form on each catkin. C, Enlarged staminate flower containing several anthers (a); b, sepals. D, Single pistillate flower with rough stigma at a.
FUNDAMENTALS IN NUT BREEDING

   Complete pollen control is vital to efficiency in nut hybridization work. The chief genera grown in this country are walnut, hickory (including the pecan), filbert, pistache, chestnut, almond, and tung. With the exception of almond and pistache, all are monoecious; that is, the pollen and nut-producing flowers form separately in different parts of the same tree, as shown for the pecan in figure 9. The almond bears perfect flowers; that is, stamens and pistils occur in the same flowers, as shown in figure 10. The pistache is dioecious and bears the pistillate and staminate flowers on different trees. In general appearance the tung flowers greatly resemble those of the almond, but they are imperfect, as stamens appear in some flowers and pistilsin others. The pollen of almond and tung trees is carried by insects; that of the walnuts, hickories, filberts, pistaches, and chestnuts is carried by wind.

In most wind-pollinated nut-bearing species, dichogamy exists to a greater or less extent. This development and maturity of the staminate (male) and the pistillate (female) flowers at different times necessitates cross-pollination. The degree of dichogamy varies with the variety, the age and nutrition of the tree, and seasonal conditions. In the case of some varieties of the same or different species, dichogamy is so complete that the trees are unfruitful unless they are pollinated by another variety producing pollen at the time the pistils are receptive. Some varieties are protandrous, that is, mature their pollen in advance of the period of stigma receptivity of the pistillate blossoms; while others are protogynous, that is, the stigmas of the pistillate flowers are receptive before pollen is matured.  In other varieties there is a short and inadequate overlapping period of pollen shedding and stigma receptivity. Therefore, the degree of dichogamy in the material worked is of considerable importance in nut-breeding operations and technique. In the case of the protandrous yarieties pollen must be so collected and stored that it will retain its viability until it can be used for selfing or for pollinating other varieties with later pistillate blossoms. The protogynous varieties present a different problem in that the development of the staminate flowers must be forced by cutting off catkin-bearing shoots and storing them in water in a warm place, or by obtaining pollen from localities where the varieties blossom earlier in the season.

Procuring pollen is quite easy, since all that is necessary is to collect the mature catkins just prior to the liberation of their pollen and to place them on smooth, hard paper in a warm, dry room, where the locules will soon open and release the pollen.

StopTheGestapo
Figure 10.—Essential parts of an almond blossom: a, Stigma; b, style; c, ovary; d, anther; e, filament.

   The stage of maturity of pollen can be determined by the stiffness of the catkins and the color of the anthers. Woodroof and his coworkers (49) found that a pecan catkin that will not shed pollen within 48 hours is relatively stiff, while one that will do so in 12 hours is limber. The color of the anthers until within about 48 hours of the time when they will begin shedding pollen is about the same as that of the leaves and bracts. After that the green color is gradually replaced by the orange yellow of the pollen. This description of pecan catkins applies in general to those of other species of Hicoria as well as to Juglans, Corylus, and Castanea.

In order to get a controlled cross it is necessary to use unmixed pollen. This is probably best procured by collecting mature catkins shortly before any pollen has been shed, washing them repeatedly with running water, removing the excess water with « sterile towel, and then drying the catkins slowly in a desiccator or other similar container. The catkins should not be too green, as they will be likely to wilt without shedding, or the viability of the pollen may become impaired.

With some species pollen loses its vitality quickly. In making crosses it is not infrequently necessary to preserve pollen for some time while waiting for the pistillate flowers of desired varieties to mature. To do this successfully, pollen; that is thoroughly dry, yet fresh, must be placed in vials or tubes plugged with cotton and held at a low but not freezing temperature.

StopTheGestapo
Figure 11.—Instrument consisting of a hypodermic needle attached to a rubber bulb by means of a curved glass tube, used by pecan breeders in applying pollen to the stigmas of pistillate flowers enclosed within cellophane covers.

Numerous methods have been used for controlling pollination in the wind-pollinated nut plants. Absolute control in such cases is quite difficult and requires a special technique not needed with insect-pollinated plants. It is essential that the pistillate blossoms be covered well in advance of their receptivity with a material that will preclude pollination. These covers must not be removed, even momentarily, while there is pollen in the air. In the pecan it has been shown that pollen is not shed when the relative humidity is about 85 percent; however, that does not insure that the air is free of pollen, for the reason that it may not have had time to settle out. Woodroof (47) found that the usual methods of covering the pistillate flowers with cloth bags or paper sacks do not eliminate all possibility of the entrance of pollen. Their findings were later supported by investigations of Traub and Romberg (40). These latter workers devised a method of using closely woven cloth bags impregnated with paraffin to cover the pistillate blossoms. A hypodermic needle attached to a rubber bulb (fig. 11) was used to introduce the desired pollen by simply pushing the needle through the cloth bag and lightly squeezing the bulb to force out the pollen. They also found that if the covers were removed and the blossoms pollinated between 5 and 7 a. m., when the relative humidity was about 85 percent, there was little danger of contamination. Later Smith and Romberg (34) improved the method by using transparent cellophane bags made from sausage casings. Since this method of pollination control is readily adaptable to all walnut and hickory species, it will be described in some detail. Cellophane sausage casings are made in many different sizes; usually a casing 1⅛ inches in diameter is satisfactory. These casings are seamless tubes, usually sold in lengths of approximately 32 feet. They are cut to the length desired, and one end is closed by tying, folding over, and tying again.  The finished case or tube should be 4 to 5 inches long. The tubes are placed over the clusters of pistillate flowers well before the stigmas become receptive. A plug of cotton batting is wrapped around the blossoming shoot so that the lower end of the tube can be tied over it (fig. 12). The cotton plug provides ventilation for the pistillate flowers. When the stigmas become receptive they are pollinated with the desired pollen by pushing the hypodermic needle through the plugs and blowing pollen over the stigmas by pressure on the rubber bulb in which the pollen has been placed. Separate needles and bulbs must be used for each variety of pollen, or if the same outfit is used it must be sterilized with 95-percent ethyl alcohol and carefully dried when changing from one variety of pollen to another. Pollination control in the almond is quite simple. The flowers are emasculated by the removal of the stamens and petals before any pollen is shed. In practice the emasculated flowers are usually covered with manila bags, or the trees are enclosed in tents or cages made of muslin or wire screen of fine mesh, to prevent the introduction of foreign pollen by insects. However, these safeguards are probably unnecessary, since in rosaceous fruits, including the almond, there is practically no wind pollination and insects do not visit emasculated flowers. When the stigmas of the almond are receptive they are pollinated by being dusted with the desired pollen applied with a camel’s-hair brush.

StopTheGestapo
Figure 12.—Cellophane cover cut from a sausage casing, used in preventing unwanted pollen from reaching the stigmas of pistillate pecan flowers to be used in breeding. This is plugged with cotton at the lower end and tied tightly at the upper end. The pollen is applied by means of a hypodermic needle (fig. 11) driven through the cotton.
STIGMA RECEPTIVITY, POLLEN SHEDDING, AND POLLEN VIABILITY

There are no available data for some of the species of nut-producing plants on the period of stigma receptivity, the time of pollen shedding and pollen viability, and the factors affecting them. In some cases investigations on these points are under way but incomplete.

The almond has a relatively long blossoming period, especially if the time is counted from the opening of the first blossoms of the earliest varieties to the last shedding of pollen by the latest varieties. Tufts and Philp (41) report that in practically all instances the first pollen produced was found inferior in quantity and in viability to that produced later by blossoms on the same trees. The abundance and viability of pollen was found to vary with the variety and from season to season, but generally pollen was abundant and viable. The viability of pollen was found to be greatly affected by wind, cold, and rain.

The filbert normally has a long blossoming period, often extending, within the same variety, for more than a month, although when temperatures are unseasonally high it may be short. According to Schuster (32), either the filbert stigmas are receptive long before they attain full size or pollen that lodges on their surfaces remains there in viable condition until the stigmas become receptive. The quantity of filbert pollen produced varies greatly according to variety, temperature, and vigor and general condition of tree, and no doubt it is influenced by other factors. The catkins begin to form in summer, and there is great danger of their being injured or killed during the following winter. For these reasons filbert pollen often shows great differences in viability. Schuster found that pollen stored in an open vessel lost less than 25 percent in viability in 2 weeks.

Normally the pecan, as well as other species of Hicoria, produces enormous quantities of pollen. Young trees generally produce catkins for one or more years before any pistillate blossoms are formed.  Woodroof (49) reports that a single pecan catkin will normally shed pollen for 2 days, a single tree for 5 to 6 days, and a single variety for 10 or 12 days. Conditions that are optimum for pollen shedding tend to be destructive to its viability.

In order to gain some idea of the quantity of pollen produced by a single pecan tree, Woodroof (48) made detailed observations and counts on a 13-year old Mantura tree that had a total of 941 shoots on which there were 44,885 catkins. These catkins had approximately 14,241,334 anthers that contained an average of 2,064 pollen grains each. The estimated number of pollen grains produced by the tree, therefore, was 29,394,113,376. He points out that had it been possible for each pollen grain to produce a nut, this tree would have supplied sufficient pollen for slightly more than 229,000 tons of nuts.

The viability of pecan pollen varies greatly with varieties, seasonal conditions, and other factors. Some years a high percentage of the pollen is defective, while in others it is mostly viable. Woodroof (49) stored pollen of 20 varieties under 10 different conditions of temperature and humidity and reported that "no temperature and humidity condition was found under which pollen could be stored for longer than 96 hours with certainty of germination," Smith and Romberg (34) report that Success pollen from a healthy, vigorous tree, stored at laboratory temperatures for 12 days, still gave a set of nuts, but that under similar conditions Schley pollen remained viable for only 8 days.

Under the humid conditions of Georgia the normal period of stigma receptivity of pecans was shown by Woodroof (49) to be about 5 days, but he pointed out that in rainy or cloudy weather the stigmas might remain receptive for 10 to 15 days. Smith and Romberg (34, 35) found that under the relatively dry conditions of Texas this period ranged from 12 to 28 days. All unpollinized nuts were found to drop in 5½ to 6½ weeks after the last receptive date.

Walnuts also produce enormous quantities of pollen. Wood (46) working with the Persian walnut found that in dry California a single catkin produced from 1 to 4 million pollen grains, and that a single tree would produce from 1½ to 40 billion pollen grains in a single season. A single stigma has a surface area of 10 to 50 square millimeters, yet he found the average number of pollen grains distributed per square millimeter per 24 hours, when pollen shedding was at its height, to be as follows:
Directly under the treesNumber
60 feet from nearest tree8.0
150 feet from nearest tree4.0
500 feet from nearest tree2.9
1000 feet from nearest tree1.0
½ from nearest treeNone


Woodroof (49) on the other hand, found that in humid Georgia, pecan pollen was carried in appreciable quantities for a distance of 3,000 feet, which would indicate that pecan pollen is lighter than walnut pollen and may be carried considerably farther.

Individual walnut catkins were found by Wood to shed pollen during 4 to 6 days, but under conditions of hot, sunny weather, such as normally prevails in the interior valleys of California at the time walnuts are in bloom, shedding is often limited to 1 day. There is a rather wide range in the development of the different catkins on the same tree, and therefore the pollen-shedding period is much longer than the time indicated for a single catkin. Wood (46) found great variation in the viability of walnut pollen. Some pollen grains were devoid of protoplasmic content, and others that appeared normal failed to germinate. The percentages of germinating pollen grains for different varieties varied from 0 to 80 percent, the average being 23 percent. Under field conditions the Persian walnut pollen loses its viability within a few days after being shed from the anther. Artificially it may be preserved best when kept in glass vials stoppered with cotton and containing a small piece of the catkin to supply moisture to the air in the vial. When kept in this manner and stored in a cool, dry place, in many instances it remained fit for artificial pollination for 3 or 4 weeks. In other cases viability was completely lost within 2 weeks.

Walnut stigmas usually remain receptive for several days, depending largely upon weather conditions. Wood (46) obtained the best results from the application of pollen when fluid was being secreted by the glandular portions of the stigmatic surface.

FERTILIZATION OF OVULE AND DEVELOPMENT OF EMBRYO

Among nut-producing plants, with the exception of the filbert, pecan, pignut, and Persian and Manchurian walnuts, very little is known regarding pollen-tube growth, ovule fertilization, or embryo development. Even in the case of the species studied there is not complete accord in the conclusions reached by different workers, and such information as is available is far from complete.

According to Benson (7), the filbert pollen grain germinates by developing a short tube, which enters the basal region of the stigma. ere the sperm nuclei enter a resting stage, remaining in this condition for 4 to 5 months. During this time the megaspore completes its development, after which the pollen tube resumes its growth and the fertilization of the egg occurs.

According to both Billings (8) and N. C. Woodroof (50), numerous pecan pollen grains germinate on the surface and send tubes into the stigmatic tissue. The tubes do not enter the stylar canal but grow downward in the tissue on each side of the micropyle and enter the Ovary cavity at a point nearly opposite the chalaza. The pollen tubes enter the cavity from 6 to 12 hours after pollination, but they do not enter the embryo sac until about 2 weeks later. The actual fusion of the egg and male nuclei probably occurs about 2 to 3 weeks later, or from 8 to 9 weeks (2, 50) after pollination. The first division of the fertilized egg occurs about 2 or 3 weeks later, or about 2 months after pollination.

Shuhart (33) reported that pecan pollination generally takes place at the time of the differentiation of the eight nuclei of the embryo sac, and that fertilization takes place about 2 weeks later. However, the Stage of embryo-sac development at the time of pollination varies greatly with seasonal conditions and to some extent with the variety. Langdon (20) reports that in the pignut, Hicoria glabra (Mill.) Britton, a megasporocyte has reached the megaspore stage or one of the early stages in gametophyte development at the time of pollination. The interval between pollination and fertilization is from 16 to 18 days, while the first division of the fertilized egg occurs about 3 weeks after fertilization or 5 weeks after pollination. In the pecan N.C. Woodroof (50) reports the first division of the egg at 8 to 9 weeks after pollination, and Shuhart (33) 3 to 4 weeks. Nast (22) found that the complete development from the megaspore mother cell to the one-celled embryo in the Persian walnut, Juglans regia, occurs within 7 to 12 days, depending on the season and climatic conditions. Fertilization of the ovule was found to take place 2 to 5 days after pollination.

In the Manchurian walnut Juglans mandshurica, it is reported by Langdon (20) that the megasporocytes pass through the different phases of meiosis within 3 to 4 days and the embryo sacs are in one of the earlier stages of nuclear division at the time of pollination. After pollination from 4 to 5 days are required for the pollen tubes to reach the embryo sacs, and fertilization of the eggs occurs 1 day later. She found that the fertilized eggs had not divided 12 days after pollination but in material collected 5 days later or 17 days after pollination four 8-celled embryos were present.

Chromosome counts have been made for a number of the nut- producing species, and these are given in table 1, in the appendix.

INCOMPATIBILITY

Except in the almond and the filbert, incompatibility, or inability of male and female cells to unite and form a fertilized egg that can grow to maturity, has not been definitely shown to exist between individuals within a variety, or between different varieties, or between species of the same genus of the nut-producing plants of the United States.

Tufts and Philp (41) found that at least in certain years all almond varieties studied were self-sterile. Of many thousand reciprocal crosses made by them, only the IXL x Nonpareil and Languedoc X Texas seemed to show distinct evidence of incompatibility or intersterility. The parentage of almond varieties now grown in the United States is unknown, and it is therefore not possible to determine whether relationship is a factor in this incompatibility between varieties. Since these few cases of intersterility have been definitely established, it is reasonable to assume that future investigations will disclose further instances of this kind.

In some cases chestnut trees, particularly of the American sweet species, Castanea dentata, that grow at a distance from others have been observed to yield unsatisfactory crops or are unfruitful, although producing staminate and pistillate flowers. Such trees apparently require cross-pollination to insure fruitfulness. This is especially true on the Pacific slope, where isolated trees that are fruitful are said to be rare. Stout (37) reports observations made on two chestnut trees growing apart from each other at Claremont, Calif., in which the trees were heavily loaded with burs, but those of one tree contained only shriveled nuts without kernels or embryos, and in the several bushels of burs from the other tree there were only about 30 nuts that contained kernels.

Self-unfruitfulness in the chestnut, especially the American species, may be due to either self-incompatibility or to dichogamy. The former condition is indicated by the report of Powell (26) in which he suggests that the pistillate flowers are probably pollinated by the staminate blossoms produced on long, slender axillary catkins, which blossom first, and also by those that are produced at the distal end of the pistillate catkin and blossom later. He also reports having noticed that most of the stigmas of both European and Japanese varieties are receptive while the early staminate flowers are in bloom.

Schuster (32) found that all varieties of filbert investigated by him are practically self-incompatible. While a planting of a single variety will generally produce a few nuts, the quantity attaining maturity is negligible in proportion to the number of pistillate blossoms. Cross-incompatibility was found to exist between a number of varieties. As with the almond, the parentage of the varieties of filbert now grown is uncertain, and therefore no correlation between relationship and. cross-incompatibility can be made. Schuster found Du Chilly, which is of the species Corylus avellana, to be cross-incompatible with C. colurna. He also found C. colurna to be nonreceptive to pollen of either Barcelona or Nottingham, both of which are of the same species as Du Chilly. Du Chilly and Barcelona were unfruitful when pollinated with C. californica. Reed (1) reported that the filbert breeding work of the late J. F. Jones showed that a large number of varieties of the European filbert, C. avellana, were definitely unfruitful and none were found to be fruitful when pollinated with pollen of Rush, C. americana, but the reciprocals of these crosses were highly fruitful. Reed (27) has reported successful pollination of Rush and Little page varieties of the American hazel with pollen of C. colurna, OC. maxima, and C. heterophylla.

INHERITANCE OF CHARACTERS

Most if not all varieties of the nut-producing species as they are grown in the United States are genetically in a complex heterozygous condition. This is due to the fact that all varieties of certain species are self-incompatible, requiring cross-pollination in order to set fruits; or they are dichogamous to a greater or less degree. Thus the nut- producing species do not lend themselves to a study of the inheritance of characters. In most cases several years’ time must elapse from the planting of the seed until the resulting seedling produces fruit, and each plant at the time of fruiting requires a considerable area of land, which greatly limits the number of individuals that can be grown under uniform conditions. Nevertheless nut improvement through breeding by hybridization and selection has tremendous possibilities for those who have the inclination, the time, and the facilities to carry on the work.

Very little is known regarding the inheritance of characters in any of the nut-producing species. Some study of hybrids between varieties has been made in the case of the almond, and of hybrids between Species in the case of the chestnut. Since 1923 the Bureau of Plant Industry and the California Agricultural Experiment Station have been cooperating in an extensive almond-breeding project. Although the total number of almond trees grown in this project has been large, the number of individuals from any one cross is too small to establish definite genetic ratios with accuracy. However, many interesting facts have been recorded. The factor for bitterness in the nut appears to be present as a recessive in all varieties of sweet almond. In most Instances when two sweet varieties are crossed, about three-fourths of the progeny will produce sweet nuts and the rest bitter nuts, giving a genetic ratio of 3:1.- In some crosses, however, the ratio is apparently 1.5:1 or 1:1. Other ratios may be found as the breeding work progresses. The factor for “red spider resistance" seems to be present in some varieties and not in others. To date, red spider-resistant progenies have resulted only from crosses involving Harriott, Eureka, Golden, Nugget, Nonpareil, and Reams. In Jordan the factor for hard shell seems to be dominant. The desirable factor of heavy bearing and the undesirable one of double kernels come out strikingly in Lewelling. From a practical standpoint the results to date show that a prime prerequisite for successful improvement in the almond by hybridization includes the discriminating selection of parents that possess outstanding characters of merit.

Beginning in 1894 and continuing for many years, Van Fleet (42) grew many chestnut seedlings from seeds produced by hybridizing Castanea dentata, C. pumila, C. sativa, C. crenata, and varieties of these species. Detailed records were not kept, but his work showed certain things of great importance to the chestnut breeder. Hybrids between the chinquapin, C. pumila, and the Asiatic chestnut, C. crenata, often produced nuts the second year after planting the seed. Apparently the habit of C. dentata of coming into bearing much later appeared in hybrids between this species and C. crenata or C. sativa, since they rarely set burs until they were 5 to 12 years old. Resistance to chestnut blight, Endothia parasitica (Murr.) P. J. and H. W. Anderson, was found only when the Asiatic chestnut was used as a parent, and even then when either C. dentata or C. sativa was a parent the progeny was susceptible. The chinquapin is measurably resistant to blight, but when it was crossed with C. sativa or C. dentata the progeny was readily susceptible. Detlefsen and Ruth (12) made studies of various taxonomic characters in three generations of chestnut trees resulting from C. dentata X C. crenata crosses made and grown by George W. Endicott, of Villa Ridge, Ill. The striking variations shown by the progeny indicate that many factors are concerned in the inheritance of the characters observed.

So far as is known, the only comprehensive attempt made to improve the European filbert, Corylus avellana, by hybridization was by C. T. Brixey, of Gervais, Oreg., who grew about 5,000 seedling trees, mostly from seeds produced by controlled cross-pollination. Out of these, only one seemed worthy of propagation. He named this Brixnut. Only first-generation seedlings were grown, and no effort was made to determine the dominance or recessiveness of the parental characters. Of approximately 2,500 controlled crosses made in the East by Reed (27) in 1927 between varieties of this species, because of cold injury only about 50 seedlings have survived. No study of inheritance has been possible.

Reed (27) reports that hybrids between Corylus americana and C. avellana seem to be much more hardy than the pollen parents and are less inclined to sucker, more erect in habit of growth, more vigorous, and more easily trained to tree form than are the pistillate parents. The foliage of the trees is usually like that of the pollen parents, as the leaves are thicker, darker, and stiffer than those of the pistillate parents. The size, form, color, thickness of shell, and plumpness and appearance of kernel are much like those of the pollen parent. The Rush variety, which was principally used as the pistillate parent, has the highly undesirable character of not permitting training to a single stem. The great majority of the hybrids yield satisfactorily to the single-stem method of training.

Although hybridization of pecan varieties has been carried on for several years by the Bureau of Plant Industry and by pecan growers, very little is known about the inheritance of characters. In most cases only first-generation hybrids have been grown; however, it seems that in cases where one of the parents is susceptible to pecan scab the progeny are likewise susceptible with few if any exceptions. Furthermore, the character of a speckled seed coat, which is characteristic of the variety Brooks, appears in most of the progeny in which Brooks is one of the parents.

The only study known to the writers of inheritance of characters in the genus Juglans is that of Babcock (4), who studied the inheritance of the peculiar oaklike character of J. californica var. quercina Babcock in progenies from controlled crosses. The first-hybrid generation seedlings. were all typical J. californica trees, and of 18 second hybrid generation seedlings grown, 12 were J. californica and 6 were J. californica var. quercina, or a ratio of 2:1. Later backcrosses of the first generation on quercina gave approximately 1:1 segregation (unpublished). Because of a widespread belief that the quercina type was the result of natural crosses between J. californica and Quercus agrifolia Nee., many controlled crosses were attempted between these species without any fruit being produced. Thus Babcock concludes that the variety quercina probably originated as a mutation.

LITERATURE CITED

 (1)  Anonymous.  1924. NORTHERN NUT GROWERS IN FIFTEENTH ANNUAL SESSION. Amer. Nut Jour. 21: 36, 39.
 (2)  Adriance, G. 1931. FACTORS INFLUENCING FRUIT SETTING IN THE PECAN. Bot. Gaz. 91: 144-166, illus.
 (3)  Babcock, E. B. 1915. WALNUT MUTATION INVESTIGATIONS. Natl. Acad. Sci. Proc. 1:35-537.
 (4)  ―1916. STUDIES IN JUGLANS. 11. Calif. Univ. Pubs., Agr. Sci. 2: 71-80, illus.
 (5)  Bailey, L. H. 1917. CHESTNUTS. His Standard Cyclopedia of Horticulture, v. 2, pp. 742-746, illus.
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 (8)  Billings, F. H. 1903. CHALAZOGAMY IN CARYA OLIVAEFORMIS. Bot. Gaz. 35: 134-135, illus.
 (9)  Bisset, P. 1914. THE JAMES RIVER WALNUT. Jour. Heredity 5: 98-101, illus.
(10)  Darlington, C. D. 1928. STUDIES IN PRUNUS, I AND II. Jour. Genetics 19: [213]-256, illus.
(11)  Darlington, C. D. 1930. STUDIES IN PRUNUS, I. Jour. Genetics 22: [65]-93, illus.
(12)  Detlefsen, J. A., and Ruts, W. A. 1922. AN ORCHARD OF CHESTNUT HYBRIDS. Jour. Heredity 13: 305-314, illus.
(13)  Forkert, C. 1914. TWELVE YEARS’ EXPERIENCE IN HYBRIDIZING PECANS. Natl. Nut Growers’ Assoc. Proc. 13: 28-30.
(14)  Fuller, A. S. 1896. THE NUT CULTURIST: A TREATISE ON THE PROPAGATION, PLANTING AND CULTIVATION OF NUT-BEARING TREES AND SHRUBS, ADAPTED TO THE CLIMATE OF THE UNITED STATES. 289 pp., illus. New York.
(15)  Graner, E. A. 1935. NOTES ON THE CHROMOSOME NUMBER AND MORPHOLOGY IN ROOT TIPS OF TUNG (ALEURITES FORDI, HEMSL.). Arch. Inst. Biol. Veg. 2: 81-82, illus.
(16)  Heiges, S. B. 1896. NUT CULTURE IN THE UNITED STATES. 144 pp., illus. U.S. Dept. Agr., Div. Pomology (unnumbered pub.).
(17)  James, S. H. 1895. A PECAN GROVE IN LOUISIANA. A PROMISING INDUSTRY. Rural New Yorker 54: 258-259.
(18)  Jaretzky, R. 1930. ZUR ZYTOLOGIE DER FAGALES. Planta, Arch. Wiss. Bot. 10: [120]-137, illus.
(19)  Kobel, F. 1927. ZYTOLOGISCHE UNTERSUCHUNGEN AN PRUNOIDEEN UND POMOIDEEN. Arch. Jul. Klaus-Stift. Vererbungsforsch. Sozialanthropol. Rassenhyg. 3: 1-84, illus.
(20)  Langdon, L. M. 1934. EMBRYOGENY OF CARYA AND JUGLANS, A COMPARATIVE STUDY. Bot. Gaz. 96: 93-117, illus.
(21)  LeLong, B. M. 1897. CALIFORNIA WALNUT INDUSTRY. Calif. State Bd. Hort. Rept. 5:77-120, illus.
(22)  Nast, C. G. 1935. MORPHOLOGICAL DEVELOPMENT OF THE FRUIT OF JUGLANS REGIA Hilgardia 9: 345-362, illus.
(23)  Nebel, B. 1931. CYTOLOGICAL ASPECTS OF BREEDING NuTs. North. Nut Growers’ Assoc. Proc. 22: 22-24.
(24)  Okabe, S. 1927. CYTOLOGICAL STUDIES ON PRUNUS (A PRELIMINARY NOTE). Bot. Mag. [Tokyo] 41: 398-404, illus. [In Japanese. English résumé, p. 404.]
(25)  ―1928. ZUR CYTOLOGIE DER GATTUNG PRUNUS. Téhoku Imp. Univ. Sci. Rept. 3: 733-748, illus.
(26)  Powell, G. H. 1898. THE EUROPEAN AND JAPANESE CHESTNUTS IN THE EASTERN UNITED STATES. Del. Agr. Expt. Sta. Bull. 42, 35 pp., illus.
(27)  Reed, C. A. 1936. NEW FILBERT HYBRIDS. Jour. Heredity 27: 427-431, illus.
(28)  Rehder, A. 1927. MANUAL OF CULTIVATED TREES AND SHRUBS HARDY IN NORTH AMERICA, EXCLUSIVE OF THE SUBTROPICAL AND WARMER TEMPERATE REGIONS. 930 pp., illus. New York.
(29)  Risien, E. E. 1914. TREE BREEDING. Natl. Nut Growers’ Assoc. Proc. 13: 30-33, illus.
(30)  ―1923. AUTOBIOGRAPHY OF A TEXAS PECAN PIONEER. Amer. Nut Jour. 18:48-49, illus.
(31)  Robbins, W. W., and Ramaley, F. 1933. PLANTS USEFUL TO MAN. 428 pp., illus. Philadelphia.
(32)  Schuster, C. E. 1924. Filberts. Oreg. Agr. Expt. Sta. Bull. 208, 39 pp., illus.
(33)  Shuhart, D. V. 1932. MORPHOLOGY AND ANATOMY OF THE FRUIT OF HICORIA PECAN. Bot. Gaz. 93: 1-20, illus.
(34)  Smith, C. L., and Romberg, L. D. 1932. POLLINATION CONTROL, PERIOD OF RECEPTIVITY AND POLLEN VIABILITY IN THE PECAN. Natl. Pecan Assoc. Bull. 31: 83-87, illus.
(35)  ―and Romberg, L. D. 1933. FURTHER STUDIES ON PERIODS OF RECEPTIVITY AND POLLEN VIABILITY IN THE PECAN. Natl. Pecan Assoc. Bull. 32: 49-55.
(36)  Smith, R. E., Smith, C. O., and Ramsey, H. J. 1912. WALNUT CULTURE IN CALIFORNIA. WALNUT BLIGHT. Calif. Agr. Expt. Sta. Bull. 231, pp. [119]}-398, illus.
(37)  Stout, A. B. 1926. WHY ARE CHESTNUTS SELF-FRUITLESS? Jour. N. Y. Bot. Gard. 27: 154-158, illus.
(38)  Taylor, W. A. 1905. PROMISING NEW FRUITS. U.S. Dept. Agr. Yearbook 1904: 399-416, illus., 1905; 1908: 473-490, illus., 1909.
(39)  ―and Gould, H. P. 1914. PROMISING NEW Fruits. U.S. Dept. Agr. Yearbook 1913: 109-124, illus.
(40)  Traub, H. P., and Romberg, L. D. 1933. METHODS OF CONTROLLING POLLINATION IN THE PECAN. Jour. Agr. Research-47: 287-296, illus.
(41)  Tufts, W. P., and Philp, G. L. 1922. ALMOND POLLINATION. Calif. Agr. Expt. Sta. Bull. 346, 35 pp., illus.
(42)  Van Fleet, W. 1914. CHESTNUT BREEDING EXPERIENCE ... Jour. Heredity 5: 19-25, illus.
(43)  ―1920. CHESTNUT WORK AT BELL EXPERIMENTAL PLOT. North. Nut Growers’ Assoc. Proce. 11: 16-21.
(44)  Wetzel, G. 1929. CHROMOSOMENSTUDIEN BEI DEN FAGALES. Bot. Arch. 25: [257|-283, illus.
(45)  Wood, M. N. 1924. ALMOND VARIETIES IN THE UNITED states. U. 8. Dept. Agr. Bull. 1282, 142 pp., illus.
(46)  ―1934. POLLINATION AND BLOOMING HABITS OF THE PERSIAN WALNUT IN CALIFORNIA. U.S. Dept. Agr. Tech. Bull. 387, 56 pp., illus.
(47)  Woodroof, J. G. 1924. THE DEVELOPMENT OF PECAN BUDS AND THE QUANTITATIVE PRODUCTION OF POLLEN. Ga. Expt. Sta. Bull. 144, pp. 134-161, illus.
(48)  ―1930. STUDIES OF THE STAMINATE INFLORESCENCE AND POLLEN OF HICORIA PECAN. Jour. Agr. Research 40: 1059-1104, illus.
(49)  Woodroof, N. C., and Bailey, J. E. 1928. UNFRUITFULNESS OF THE PECAN. Ga. Expt. Sta. Bull. 148, 40 pp., illus.
(50)  Woodroof, N. C. 1928. DEVELOPMENT OF THE EMBRYO SAC AND YOUNG EMBRYO OF HICORIA pecan. Amer. Jour. Bot. 15: 416-421, illus.
(51)  Woodworth, R. H. 1929. CYTOLOGICAL STUDIES IN THE BETULACEAE. II, CORYLUS AND ALNUS. Bot. Gaz. 88: 383-399, illus.
(52)  ―1930. MEIOSIS OF MICROSPOROGENESIS IN THE JUGLANDACEAE. Amer. Jour. Bot. 17: 863-869, illus

APPENDIX
Table 1.—Number of somatic chromosomes in certain nut-producing plants
Common nameScientific nameSomatic chromosome number (2n)Authority1
AlmondAmygdalus communis16(10, 11, 19, 24, 25)
     Chestnut:
AmericanCastanea dentata24(18)
SpanishCastanea sativa24(18)
     Filbert:
Corylus avellana2 28(51)
Corylus avellana var. pontica28(51)
GiantCorylus maxima2 28(51)
     Hazelnut:
AmericanCorylus americana2 28(51)
TreeCorylus colurna28(51)
Corylus heterophylla28(51)
BeakedCorylus rostrata2 28(51)
JapaneseCorylus sieboldiana28(51)
TibetianCorylus tibetica28(51)
     Hickory:
BitternutHicoria cordiformis32(52)
MockernutHicoria alba64(52)
PecanHicoria pecan3 20-24(50)
PignutHicoria glabra64(52)
ShagbarkHicoria ovata32(52)
ShellbarkHicoria laciniosa32(52)
Sweet pignutHicoria ovalis64(52)
     Walnut:
BlackJuglans nigra4 32(51)
ButternutJuglans cinerea32(51)
California blackJuglans californica34(3)
Juglans californica var. quercina34(3)
JapaneseJuglans sieboldiana32(52)
ManchurianJuglans mandshurica32(52)
PersianJuglans regia4 32(52)
TexasJuglans rupestris32(52)
HeartnutJuglans sieboldiana var. cordiformis32(52)
     Tung
Aleurites cordata22(6)
Aleurites fordii22(6, 15)
1 Reference is made by number to Literature Cited, p. 957.
2 Woodworth (51) reports: “Three pairs of the gemini commonly fuse completely, so that the metaphase plate appears to have eight small chromosomes and three large ones.” In view of this fact Wetzel (44) and Jaretzky (18) reported only 11 chromosomes as the haploid number.
3 Because of the small size of the chromosomes the number has not been definitely determined; most probably the base number is the same as for the family.
4 Nebel (28) reports that the somatic chromosome number in J. regia, J. nigra, and one J. nigra X regia F1 hybrid is 34.
Table 2.—Nut species now being bred, locations, institutions, workers, and methods
SpeciesLocationInstitutionWorkersMethod1
AlmondSacramento and Davis, Calif.U.S. Department of Agriculture and State Agricultural Experiment StationMilo N. WoodS,H
Newberg, Oreg.PrivateA. B. ScherfS
Sydney, AustraliaDepartment of Agriculture, New South WalesH. WenholzS
ButternutBeltsville, MdU.S. Department of AgricultureH. L. Crane, J. W. McKay, C. A. ReedS,H
Geneva, N. Y.State Agricultural Experiment StationGeorge L. SlateS
Litchfield, ConnPrivateW.C. DemingS
Ithaca, N. Y.PrivateS. H. GrahamS
Cleveland, OHPrivateC. F. WalkerS
St. Paul, MinnPrivateCarl F. WeschckeS
Harrisburg, Pa.PrivateG. A. ZimmermanS
ChestnutGlenn Dale, MdU.S. Department of AgricultureR. B. Clapper, G. F. GravattH
Beltsville, MdH.L. Crane, J. W. McKay, C. A. ReedS,H
Urbana, ILState Agricultural Experiment StationA.S. ColbyH
Ettersburg, Calif.PrivateAlbert EtterS
Godfrey, ILAmelia RiehlS
Roanoke, VaH. F. StokeS,H
Harrisburg, Pa.G. A. ZimmermanS
FilbertBeltsville, MdU.S. Department of AgricultureH. L. Crane, J.W. McKay, C. A. ReedS,H
Corvallis, Oreg.C. E. SchusterS,H
St. Paul, MinnState Agricultural Experiment StationW.H. Alderman, Ernest Angelo, W. G. Brierly, F. E. HarolsonS
Geneva, N. Y.George L. SlateS,H
Gervais, OregPrivateC.T. BrixeyS,H
Washougal, WashD. FitzgeraldS
Salem, Oreg.Pearcy Bros.S,H
Newberg, Oreg.A.B. ScherfS
College Park, MdC.P. CloseS
Glenn Dale, MdJ.J.T. GrahamS
HickoryBeltsville, MdUSDAH.L. Crane, J.W. McKay, C.A. ReedS
Urbana, ILState Agricultural Experiment StationA.S. ColbyS
Geneva, N. Y.Geo L. SlateS
Wooster, OhioJ.H. GourleyS
Litchfield, ConnPrivateW.C. DemingS
Ithaca, N. YS.H. GrahamS
Downingtown, PaJ. W. HersheyS
Kent, OhioHomer L. JacobsS
Lancaster, PaMildred M. JonesS
Swarthmore, PaJ. Russell SmithS
Center Point, IowaSnyder Bros. Inc.S
Cleveland, OhioC.F. WalkerS
Harrisburg, Pa.G.A. ZimmermanS
PecanBeltsville, MdUSDAH. L. Crane, J. W. McKay, C. A. ReedS,H
Robson, LaF.N. DodgeS
Albany, GaMax B. Hardy, Harry LutzS
Austin, TXC.L. SmithS
Urbana, ILState Agricultural Experiment StationA.S. ColbyS
Shattue, Ill.PrivateJ.G. DuisS
O'Fallon, ILJoseph GerardiS
Harrisburg, ILH.C. NevilleS
Chetopa, KanCharles StephensS
Rockville, Mo.J. TiedkeS
Rockport, IndJ. F. WilkinsonS
Sydney, AustraliaDepartment of Agriculture, New South WalesH. WenholzS
Mexico, D. F.Secretariat of Agriculture, Department of Stations and Experimental FieldsG. GandaraS
TungGainesville, FlaState Agricultural Experiment StationHarold MowryS
Tifton, GaGeorgia Coastal Plain Experiment StationOtis WoodwardS
Baton Rouge, La.State Agricultural Experiment StationW.D. KimbroughS
Walnut, Eastern BlackBeltsville, MdU.S. Department of AgricultureH. L. Crane, J. W. McKay, C. A. ReedS,H
Urbana, ILState Agricultural Experiment StationA. S. ColbyS
St. Paul, MinnW.H. Alderman, Ernest Angelo, W. G. Brierly, F. E. HarolsonS
Geneva, N.Y.George L. SlateS
Wooster, OhioJ. H. GourleyS
Climax, Mich.PrivateGilbert BeckerS
Fayetteville, ArkN. F. DrakeS
Shattue, ILJ DuisS
O'Fallon, ILJos. GerardiS
Ithaca, NYS. H. GrahamS
Eldora, IAE. F. HuenS
Godfrey, ILAmelia RielS
Swarthmore, PAJ. Russell SmithS
Roanoke, VaH. F. StokeS
Cleveland, OhioC. F. WalkerS
Cincinnati, OhioHarry R. WeberS
St. Paul, Minn.Carl F. WeschckeS
Harrisburg, Pa.G. A. ZimmermanS
JapaneseBeltsville, MdU.S. Department of AgricultureH. L. Crane, J. W. McKay, C.A. ReedS,H
Litchfield, ConnPrivateW.C. DemingS
Westbank, B.C.J.U. GellatlyS, H
Downingtown, PaJ.W. HersheyS
Lancaster, Pa.Mildred M. JonesS
Wassaic, N. YGilbert L. SmithS
Westfield, N. Y.Ross Pier WrightS
PersianCorvallis, OregUSDAC.E. SchusterS
St. Paul, MinnState Agricultural Experiment StationW.H. Alderman, Ernest Angelo, W. G. Brierly, F. E. HarolsonH
Geneva, N. Y.George L. SlateH
Roseburg, Oreg.PrivateC. E. MoyerS,H
Mexico, D. FSecretariat of Agriculture, Department of Stations and Experimental FieldsG. GandaraS
1S=selection, H=hybridization

Table 3.—Varieties of nuts of probable value for breeding
Genus, species, variety, and regionOrigin or introducerComments
   Amygdalus communis:
DrakeCaliforniaOf chief value because of prolificacy and usefulness as a pollinizer
EurekaHighly prolific, with small but very sweet nuts.
IXLLong one of California’s most valuable varieties.
Ne Plus Ultra
Nonpareil
TexasA heavy bearer, considerably like Drake.
   Corylus:
White AvelineLong a standard; from EuropeShell very thin; kernel of finest quality and flavor.
BarcelonaLeading variety of Pacific Northwest.
BrixnutC. T. Brixey, Gervais, ORLarge nut; very prolific.
Du ChillyLong a standard from EuropeLong a chief variety in Pacific Northwest.
Italian RedLong well known; from EuropeHas given good results in eastern breeding.
LittlepageThomas P. Littlepage, Bowie, Md.A highly prolific native from southern Indiana.
RushJ. G. Rush,1 PennsylvaniaA native found highly useful in breeding.
WinklerSnyder Bros., Inc., Center Point, IowaBest native variety yet found in State.
   Hicoria (exclusive of pecan):
Anthony {probably H. ovata)A.B. Anthony, Sterling, ILAn excellent nut.
Berger (probably H. laciniosa X alba)Russell Berger, Cove Gap, Pa.First prize miscellaneous hickories, 1934 contest, Northern Nut Growers’ Association.
Chase (probably H. ovata)W.R. Chase, Hartford, Conn.An excellent nut.
Coleman (probably H. ovata)Mrs. Thomas Coleman, Saltsburg, PaThird prize, 1934 contest, Northern Nut Growers’ Association.
Davis (probably H. ovata)Dwight Davis, Dover Plains, N. YFirst prize, 1934 contest, New York State.
Emerick (probably H. ovata)Etta Emerick, West Camp, N. YSuperior cracking quality.
Fox (probably H. ovata)Roland D. Fox, Fonda, N. YFirst prize, 1934 contest, Northern Nut Growers’ Association
Goheen (probably H. ovata)Mrs. Martha Goheen, Furnace, Pa.Second prize, 1934 contest, Northern Nut Growers’ Association.
Hagen (probably H. ovata)Mrs. C. E. Hagen, Guttenberg, IowaOne of the best known in the State.
Heibner (probably ovata)Harvey A. Heibner, Danville, IowaVery superior nut.
Jolliffe (probably H. ovata)George C. Jolliffe, Uffington, W. VaVery high percentage of kernel.
Lawson (probably H. ovata)Donald Lawson, Dorloo, N. YSecond prize, 1934 contest, New York.
Mann (probably H. ovata)Mrs. Rae D. Mann, Davison, MichFirst prize, 1932 contest, Michigan.
Miller (probably H. ovata)D.P. Miller, North Branch, MichSecond prize, 1932 contest, Michigan.
Redcay (probably H. laciniosa)Adam Redcay, Lititz, PaSecond prize, miscellaneous hickories, 1934 contest, Northern Nut Growers’ Association.
Romig (probably H. ovata)Romig Bros., Downington, Pa_An excellent nut.
Sande (probably H. ovata)Elmer T. Sande, Story City, IowaOne of best known in Iowa.
Swaim (probably H. ovata)H.H. Swaim & Son, South Bend, IndHighly prolific.
Vest (probably H. ovata)Luther W. Vest, Blacksburg, VaExtremely thin shell.
Whitney (probably H. ovata)W.O. Whitney, Berea, OhioFirst prize, 1934 contest, Ohio
Wilcox (probably H. ovata)P. E. Wilcox, Geneva, OhioSecond prize, 1934 contest, Ohio.
   Hicoria pecan:
      Southeastern region:
BrakeWillian H. Brake, Rocky Mount, NCOutstanding cracking and kernel quality
BrooksB. W. Stone, Thomasville, Ga_Scab-resistant; prolific; superior cracking quality.
CandyTheodore Bechtel,1 Ocean Springs, Miss.Superior table variety; roundish
CurtisJ.B. Curtis1, Orange Heights, FlaScab-resistant; superior cracking and kernel quality.
DesirableC. Forkert,1 Ocean Springs, MissLarge size; scab-resistant; good cracking quality.
LewisF.H. Lewis,1 Pascagoula, Miss.
MobileB. W. Stone, Thomasville, GaProlific; scab-resistant.
MoneymakerS. H. James,1 Mound, La.Prolific; early to mature.
MooreSeveral nurserymen, Monticello, Fla.Prolific: scab-resistant; early; good cracking quality.
NelsonWilliam Nelson,1 New Orleans, LaProlific; vigorous; scab-resistant.
RussellH. F. Russell,1 Ocean Springs, Miss.Scab-resistant; very thin shell; sweet.
SchleyA. G. Delmas,1 Pascagoula, MissThin shell; very superior kernel quality.
StuartW.R.Stuart,1 Ocean Springs, Miss.Scab-resistant; of good commercial size.
SuccessTheodore Bechtel,1 Ocean Springs, Miss.One of the best when good; variable.
      Southwestern region:
BurkettJ. H. Burkett, Clyde, Tex.Very fine table variety.
ClarkWilliam Millican, Bend, TexVery fine all-around variety.
HalbertH. A. Halbert,1 Coleman, Tex.Extremely precocious and prolific.
NuggetJ. A. Evans, Arlington, Tex.Superior shelling quality.
San Saba ImprovedE. E. Risien & Son, San Saba, Tex.Notably thin shell.
SovereignNotably prolific.
SquirrelNotable flavor.
SupremeGenerally very fine variety.
Western
      Northern region:
BusseronLong a standard; from near Vincennes, Ind.Matures early; no other advantage.
ClarksvilleArthur L. Norton, Clarksville, MoOne of the most northern in origin.
DewittGeorge F. Dewitt, Butler, MoSuperb cracker; high a percentage kernel.
DuleyJohn Duley, New Haven, IllVery good all-around nut.
ElmerSnyder Bros., Inc., Center Point, IowaShould be one of the most hardy.
FisherJoseph Gerardi, O'Fallon, ILSaid to be unusually prolific.
GallatinW. Richardson, New Haven, ILOne of the most promising new varieties.
GoforthBert Goforth, New Haven, Ill.First prize, 1934 contest, Northern Nut Growers’ Association.
GreenriverStandard variety; Daviess County, KYBest of older northern varieties.
HarmonAnna S. Harmon, Mount Carmel, IllAn excellent seedling, not yet propagated.
HofmannO. J. Hofmann, Henderson, KyAn excellent seedling, not yet propagated.
IndianaLong a standard; 300 yards from original Busseron.Matures early; no other advantage.
KentuckyLong a standard; northern KentuckyExcellent midseason pollinizer.
MajorLong a standard; Daviess County, KyExcellent nut, but too small and round.
MeyerMrs. Tony Meyer, Brunswick, MoShould be hardy well north.
NiblackM. J. Niblack,1 Vincennes, IndBest cracking quality; very sweet.
NortonArthur L. Norton, Clarksville, MOLarge nut; should be hardy north.
PoseyLong a standard; southwestern IndianaHandsome tree; excellent cracker.
SeptemberJ. F. Wilkinson, Rockport, IndSaid to be earliest to mature.
   Juglans cinerea
AikenJ. F. Jones Nurseries, Lancaster, PaFrom New Hampshire; small but good cracker
AlversonM. E. Alverson, Howard City, Mich.Third prize, 1932 contest, Michigan.
BakerG. A. Zimmerman, Harrisburg, Pa.From New York; highly promising.
BuckleyPark Buckley, Strawberry Point, IowaOne of best known in Iowa.
DeVanF. E. DeVan, Rock Creek, OhioFifth prize, 1929 contest, Northern Nut Growers’ Association.
HostetterC. F. Hostetter, Bird in Hand, Pa.Third prize, 1929 contest, Northern Nut Growers’ Association.
IrvineL. K. Irvine, Menomonie, Wis.First prize, 1929 contest, Northern Nut Growers’ Association.
KenworthyJohn F. Kenworthy, Rockton, WisFourth prize, 1929 contest, Northern Nut Growers’ Association.
LingleE. J. Lingle, Pittsfield, PaSixth prize, 1929 contest, Northern Nut Growers’ Association.
LoveCharles P. Reed, Howell, Mich.One of best known in Michigan.
LutherF. Luther, Fairgrove, Mich.Second prize, 1932 contest, Michigan.
MitchellClaude Mitchell, Scotland, Ontario, Canada.First prize, 1932 contest, Michigan.
RobinsonMrs. Ada Robinson, Waterman, ILOne of best known in Illinois.
SherwoodSnyder Bros., Inc., Center Point, IAOne of best in State.
SmithHorace T. Smith, Chicopee, MAOne of best known in Massachusetts.
TheadeM. F. Thede, Wayland, MIOne of best known in Michigan.
ThillM. J. Thill, Bloomer, Wis.Second prize, 1929 contest, Northern Nut Growers’ Association.
UtterbackW.E. Utterback, Sigourney, IowaOne of best in State.
WrightDouglas N. Wright, Colchester, VtOne of best known in State.
   Juglans nigra
AdamsR. Adams, Scotts, Mich.Highly rated by U.S. Department of Agriculture and Michigan Agricultural Experiment Station.
AllenGlenn W. Allen, Middleville, Mich.
AsburyC.D. Asbury, Augusta, KyThird prize, 1926 contest, Northern Nut Growers’ Association.
BentonW. A. Benton, Wassaic, N. YSecond prize, 1934 contest, New York.
BoothR. A. Booth, Bonsack, VaExcellent cracking and kernel qualities.
BrownMrs. Willard Brown, Rock Bridge, OhioFirst prize, 1933 contest, Ohio.
ClarkFrank Clark, Lamoille, MinnFourth prize, 1934 contest, Northern Nut Growers’ Association.
CowleB. A. Cowle, Defiance, OhioThird prize, 1933 contest, Ohio.
CreitzW. A. Creitz, Cambridge City, IndExcellent cracking and kernel qualities.
CrescoW. A. Bents, Cresco, IowaVery good nut; very hardy.
DoughertyL. D. Dougherty, Crane, Mo.Very good nut; best for southern latitudes.
EdgewoodBen F. Walker, Siloam Springs, Ark.
EdmundsLewis Edmunds, Glasgow, KyFirst prize, 1934 contest, Northern Nut Growers’ Association.
EdrasGerald Adams, Moorhead, IowaHigh percentage of excellent kernel.
FranklinG. A. Zimmerman, Harrisburg, PAGood nut; blooms very late.
FreelMrs. E. W. Freel, Pleasantville, IAFirst prize, 1929 contest, Northern Nut Growers’ Association.
GrundyJohn Rohwer, Grundy Center, IowaFirst prize, Iowa State Fair, 1927.
HeplerGeorge Y. Hepler, South Bend, IndExcellent cracking and kernel qualities.
ImpitJ. U. Gellatly, Westbank, British Columbia, CanadaFor consideration in Pacific Northwest.
JansonW. W. Janson, Jefferson, OhioFourth prize, 1933 contest, Ohio.
KettlerFred Kettler, Platteville, Wis.Excellent nut; should be hardy in North.
KnapkeJ.J. Knapke, New Weston, OhioExcellent nut; high percentage of kernel.
LearnDane Learn, Aylmer, Ontario, CanadaVery white kernel; very sweet; hardy.
LeeR. E. Lee, Troutviile, Va.One of best yet found in Virginia.
LionbergerJohn W. Lionberger, Table Rock, Nebr.Best yet found in State; very good nut.
MarionMrs. E. W. Freel, Pleasantville, IowaFirst prize, 1929 contest, Northern Nut Growers’ Association.
McMillanLowell McMillen, Buchanan, Mich.Excellent cracking and kernel qualities.
McPhersonA. McPherson, Jr., Caledonia, N. Y.Third prize, 1934 contest, New York.
MintleJ. R. Mintle, Glenwood, IowaUnusually fine nut.
MontereyL. K. Hostetter, Lancaster, Pa.Excellent cracking and kernel qualities.
MyersE.R. Myers, Bellefontaine, OhioUnusually thin shell; very good otherwise.
OhioJ. F. Jones Nurseries, Lancaster, PaStandard variety since first propagated in 1915
PattersonMrs. William Patterson, Wever, IowaExcellent cracking and kernel qualities.
PinecrestHerbert Miller, Richfield, Pa.
RohwerJohn Rohwer, Grundy Center, IowaSecond prize, 1926 contest, Northern Nut Growers’ Association.
SiffordC. L. Sifford, Buchanan, VaExcellent cracking and kernel qualities.
SnyderC. H. Snyder, Newfield, N. YFirst prize, 1934 contest, New York.
SparrowHarry C. Sparrow, Lomax, ILExcellent cracking and kernel qualities.
StablerThomas P. Littlepage, Bowie, MDMany nuts have single lobes; good cracker.
Ten EyckJ. F, Jones, Lancaster, PaUnusually thin shell..
ThomasJ. W. Thomas & Sons, King of Prussia, Pa.Has long been the leading standard variety.
ThropRalph Throp, Greensburg, OhioMost or all have single lobes.
TrittenSam Tritten, Lisbon, OhioSecond prize, 1933 contest, Ohio.
WaldsmithL. O. Waldsmith, Hartselle, Ala.Best black walnut yet found in Alabama.
WandaGerald Adams, Moorhead, IowaExcellent cracking and kernel qualities.
WetzelAnnie M. Wetzel, New Berlin, Pa.Fourth prize, 1929 contest, Northern Nut Growers’ Association
WiardEverett Wiard, Ypsilanti, Mich.Third prize. 1934 contest, Northern Nut Growers’ Association.
WrightHerman Wright, Wolcott, N. YFourth prize, 1934 contest, New York.
   Juglans regia:
ConcordFrench parentageLeading favorite in central portions of California; blooms late.
Crath SeedlingsPolandNow being introduced by Paul C. Crath, Toronto, Canada, in the hope of finding greater hardiness.
EhrhardtSouth AmericaA heavy bearer of high-grade commercial nuts.
EurekaPersiaA leading commercial sort; blooms late; nuts well sealed.
FranquetteFranceLate bloomer; leading commercial sort of Pacific Northwest.
PayneVery precocious and prolific.
PlacentiaSouth AmericaThe leading commercial variety in southern California.
   Juglans sieboldiana:2
Bates (Hn)J. F. Jones Nurseries, Lancaster, PaOne of best yet tested.
Bourne (Hn)Fred Bourne, Milford, Mich.Second prize, 1932 contest, Michigan.
Calendar (Hn)J. U. Gellatly, Westbank, British Columbia, CanadaBest variety from Pacific Northwest.
Cardinell (S)Bob Cardinell, East Lansing, MichThird prize, 1932 contest, Michigan.
Caruthers (Hn)A. Caruthers, Ferrell, VaBest variety from Virginia.
English (S)Harold English, Chatham, Ontario, CanadaFirst prize, 1932 contest, Michigan.
Evers (Hn)A. H. Evers, Petoskey, MichSecond prize, 1932 contest, Michigan.
Faust (Hn)J.F. Jones Nurseries, Lancaster, PaExceptionally vigorous; good nut; large.
Fodermaier (Hn)John Fodermaier, Dover Plains, NYExcellent nut; highly promising.
King (Hn)Sonn W. Hershey, Downingtown, Pa
LancasterJ. F. Jones Nurseries, Lancaster, PaStandard; first variety propagated.
Mitchell (Hn)Claude Mitchell, Scotland, Ontario, CanadaFirst prize, 1932 contest, Michigan.
Stranger (Hn)J. F. Jones Nurseries, Lancaster, PaSaid not to be dichogamous.
Wright (Hn)Ross Pier Wright, Westfield, N. YVery new; apparently one of the best.
   Juglans sieboldiana hybrids:
Cording X J. regiaR. Bates, Jackson, S. C.Extremely rapid grower.
Creitz X J. cinereaW. A. Creitz, Cambridge City, Ind.Prolific; reasonably good.
Helmick X J. cinereaJames K, Helmick, Columbus Junction, IowaHeavy bearer; quite good.
1 Deceased.
2 Hn=heartnut; S= = Siebold walnut.

NOTES
ψPersonal statement made July 21, 1910, in Washington, D. C., by E. R. Lake, former professor of horticulture and forestry, Oregon Agricultural College, Corvallis.
†Letter from Mr. Hatch in Department file written June 20, 1892; Nut Culture in the United States (16, p. 20); and recent statement by Mrs. P. C. Campbell, Vacaville, Calif,, a daughter of Mr. Hatch.