The cherry is another very important stone fruit, although it is not grown so extensively in the United States as the peach and the plum. The varieties in which we are interested for their value as edible fruit belong to two groups, the sweet and the sour. Varieties of the former group are used principally for fresh-fruit dessert, while those of the latter make up the great bulk of the frozen and canned cherries of commerce for use in bakeries, restaurants, and homes for pies, preserves, and sauce. In fact, so important is their use for pies that this group of sour varieties is frequently referred to as pie cherries.
Unfortunately, our present-day cherry varieties are not so widely adapted over this country as we should like to have them. While the sweet cherry trees are as hardy in wood as the peach, they do not recover so well from winter injury. They blossom early in the spring, and the flowers are very susceptible to cold and frost injury. The sour cherry tree is as hardy as some apple varieties, but its blossoms are also quite tender to cold, and crops are frequently lost by spring frosts. In more southern latitudes in this country the trees do not thrive in the hot, dry summers, and in the more humid regions the fruits are very susceptible to brown rot. Chiefly because of special climatic requirements, the principal commercial production of sour cherries is limited to districts along the Great Lakes in the East, and of the sweet cherry varieties to the Pacific and Intermountain States of the West.
All varieties of cultivated cherry belong to two species (3, 18). The sweet cherries, Prunus avium L., (fig. 15) are tall trees with few or no suckers from the roots and with leaves downy on the under side. The sour cherries, Prunus cerasus L., (figs. 16 and 17) are small trees with many suckers from the roots and with fruit sour to bitter in taste.
Wild forms of the sweet cherry found growing in this country and in Europe are also called mazzard, bird, and wild sweet cherry. Some of these have escaped from cultivation.
The native habitat of the sweet cherry species is in southern and central Europe and Asia Minor. This species has been divided by botanists into different groups, but because of hybridization among the varieties it is rather difficult in many cases to classify them. Sweet cherries with soft, tender flesh form one group, known by pomologists under the French group name guigne or the English gean. These are also known as the heart cherries. These sweet, soft-fruited cherries may again be divided into dark-colored varieties with reddish juice, and light-colored varieties with colorless juice. Among the light- colored gean varieties are Coe, Ida, Elton, and Wood. Dark-colored ones are represented by Black Tartarian (fig. 18) and Early Purple. The second group is distinguished by the firm, crisp flesh of the fruits and is referred to as the bigarreaus. Windsor, Republican, Bing, and Lambert are representative varieties of the black type, while light types are Yellow Spanish and Napoleon (fig. 15).
The native habitat of Prunus cerasus seems to be close to that of P. avium in the region about the Caspian Sea to western Anatolia. De Candolle concludes that P. avium extended westward more rapidly and was the first to become naturalized. Like the sweet cherry, the sour cherry is also divided into groups based on the color of the juice. Cherries with colorless juice are the amarelles, consisting of pale-red to red fruits more or less flattened at the ends (fig. 19). Common representatives of this group are Early Richmond and Montmorency (figs. 16 and 17). The second group called the morellos, contains varieties with very dark round to oval fruits and flesh with reddish juice. Typical varieties of this group are English Morello, Ostheim, and Olivet. A third type in the species is the marasca cherry, from which is made maraschino, a liqueur used in Europe and the United States in the manufacture of maraschino cherries. The marasca cherry is a native of the Province of Dalmatia, Yugoslavia, where the trees grow wild. The fruits of the marasca varieties are much smaller and darker and somewhat more acid than the common sour cherry. In the United States at the present time some varieties of sweet cherry such as Napoleon, and some sour varieties, are being used for making maraschino cherries.
The duke cherries (fig. 20) are intermediate in type and have sometimes been referred to Prunus avium, but more recently have been considered to be hybrids between P. avium and P. cerasus. In France they are called royals. May Duke, perhaps one of the oldest varieties grown in the United States, Reine Hortense, and Late Duke are important varieties of this group. In the duke cherries many characteristics of fruit, skin, flesh, juice color, and flavor, as well as of tree growth, are intermediate between the sweets and sours.
Three other species of cherry that have been used by breeders are the Nanking or bush cherry, Prunus tomentosa Thunb., an inhabitant of central Asia; the sand cherry, P. pumila L., of the shores and beaches of the eastern United States; and the western sand cherry or Bessey cherry, P. besseyi Bailey, of the western United States.
In addition to the wild sweet or mazzard cherry, two other species are important from the standpoint of stocks on which to bud or graft varieties for propagation. These are the small wild, inedible sour cherry of southern Europe, Prunus mahaleb L., known as the mahaleb cherry, and the small wild red or pin cherry of the Northern States and Canada, P. pensylvanica L. f.
Attempts have also been made to locate pleasant-flavored strains of the chokecherry, Prunus virginiana L. Some strains are quite inedible until fully ripe.
One of the main objectives in cherry breeding is the production of high-quality sweet varieties that will prove more hardy in tree and blossom characters than many of those now available for planting. The production of such a delicious fruit as the sweet cherry is now limited to a very few regions of this country. Even in those regions where it can be grown there is need for firm-fleshed varieties that do not crack and that will ripen over a long season. At the present time we have no firm-fleshed early-ripening varieties of the bigarreau type. The unsatisfactory viability and germination of seed of early-ripening varieties impede progress in this direction at the present time.
In obtaining varieties that will be suited to regions where moderately low winter temperatures prevail, the matter of understocks may be of first importance. The chief limiting factor in growing hardy cherries in the northern Great Plains area, as well as in certain other parts of the United States, is the relative tenderness of some mahaleb and mazzard stocks used in propagation. Selection of better understocks that will prove more cold-resistant and more widely adapted than those in present use is worthy of further investigation. Selections of native cherries that appear to be better adapted to various soil and climatic conditions, such as hardier strains of our native mazzard and mahaleb stocks, may prove fruitful of results (21). Cherries are not grown at the present time in the vast area comprising the southern part of the United States, principally because of the susceptibility of our available varieties to certain diseases. There is need for the development of disease-resistant varieties for this region.
More genetic and cytological studies are needed, particularly of hybrids between the sweet and sour varieties, as a basis for more intelligent choice of desirable parents. Some of the duke varieties are very excellent cherries but they are not highly productive. Methods of inducing polyploidy in order to obtain greater fertility in cherries has received little attention.
The methods used in breeding new varieties of cherry are not different from those already discussed for the peach and the plum. Since all of the important varieties of Prunus avium have been shown to be self-unfruitful (28, 30) emasculation is unnecessary, but with the sour and duke varieties the blossoms must be emasculated.
One of the important problems confronting the cherry breeder at present is to find methods for growing the seeds of early-ripening varieties.
Breeding of new varieties of cherries does not seem to have attracted the interest of private breeders to the extent noted with peaches and plums. Interest has always been maintained in a search for new varieties, but progress in obtaining them has been slow. The failure to develop new varieties may be due partly to the fact that the cherry is not at home over such a large area of this country as the peach and the plum. The tenderness of the sweet cherry (Prunus avium) varieties, with the resulting loss of trees during cold winters, has largely limited their culture to the more protected areas along the Great Lakes and to the Pacific and Intermountain States of the West. The failure to obtain new varieties, particularly the sweet sorts, may also be due to the failure of the seed to grow.
The success obtained by two private breeders is worthy of mention. The pioneer breeding work of the brothers Henderson and Seth Lewelling in Oregon dates back to 1848 (18). In that year Henderson Lewelling carried an assortment of varieties of peach, apple, pear, plum, and cherry by wagon from Iowa to Oregon. These were planted in Milwaukie, Oreg., as a source of material for nursery and variety-improvement work. One of the most important varieties of cherry in this collection was the Napoleon. Apparently the tag had been lost and the variety was renamed the Royal Ann, the name by which it is known in the Pacific Coast States today. From this stock of Royal Ann and other cherries, three important new varieties of the black bigarreau type were developed, Republican, Lambert, and Bing. Republican, possibly a cross of Napoleon and Black Tartarian, originated as a seedling in Seth Lewelling’s orchard in 1860. Lambert originated as a seedling under a tree of Napoleon planted by Lewelling in 1848. From a seed of Napoleon planted in 1875 in Milwaukie, Seth Lewelling grew the promising seedling that later he called Bing. These excellent varieties developed by the Lewelling brothers laid the foundation for the present cherry industry in the Pacific Northwest as well as in California. The Bing, Lambert, Republican, and Napoleon are at the present time the leading commercial varieties of sweet cherry in this region.
At about the time that the Lewellings were working on the development of cherry varieties in Oregon, J.P. Kirtland, of Cleveland, Ohio, was engaged in similar work for the eastern United States. [The author, Mr. Cullinan, often misspelled Dr. Kirtland's name, calling him P.J. Kirkland, and the cherry cultivar for his daughter, so I've corrected these errors herein. -ASC] Varieties introduced by Kirtland that have been grown and are still being grown to some extent are the soft-fleshed sweet varieties Black Hawk, Kirtland, and Rockport.
In view of the results obtained by these men it is rather surprising that no enterprising breeder has become interested in more recent times in searching for better varieties and types of sweet cherries adapted to this country.
The New York (State) Agricultural Experiment Station at Geneva has done the most work on cherry breeding in recent years. The first crosses were made in 1911. To date, about 1,200 seedlings have been planted for fruiting, and in addition there are a few hundred in the nursery for future planting. Sixty-two different sweet, sour, and duke varieties and a few seedlings have been used in the breeding studies. The varieties used most extensively were Abbesse d’Oignies 33 times, Abundance 47, Bing 57, Burbank 9, Coe 16, Early Rivers 35, Early Purple 9, English Morello 46, Elton 41, Emperor Francis 45, Early Richmond 21, Giant 82, Gil Peck 15, Hedelfingen (Géante d’Hedelfingen) 27, Ida 12, Kirtland 50, Knight 10, Ludwig 27, Lambert 81, Lyons 58, May Duke 72, Montmorency 73, Napoleon 103, Ostheim 26, Olivet 14, Oswego 11, Reine Hortense 25, Royal Duke 9, Republican 32, Schrecken 30, Seneca 74, Schmidt 74, Windsor 59, Wood 24, and Yellow Spanish 54.
Unfortunately, many cherry seeds failed to germinate, and consequently from thousands of seeds comparatively few trees were obtained. The seeds of early varieties were nearly 100 percent nonviable. The Seneca, a very early black sweet cherry, was produced at the Geneva station by crossing an early unknown sweet with the Early Purple. This variety originated in 1911 and was sent out for trial in 1924. The only other seedling that has been named was derived from a cross made in 1925 between Napoleon and Giant. This seedling was named Gil Peck upon request of the Indian tribes of New York, who were very fond of the late Gilbert W. Peck, a Cornell extension worker in pomology. The Gil Peck was introduced in 1926.
The objectives of the work in New York have been the production of firm-flesh sweet cherries that do not crack or rot and that ripen from early to late season. To secure lateness, large-fruited varieties were crossed with Abundance and with a small, very late, firm-flesh cherry called Oswego. Late-blooming mazzards have also been used in order to secure later blooming varieties that may escape late spring freezes.
In addition to fruit of good quality for commercial purposes, productive hardy trees have been given consideration in this work. Little work has been done with the sour (Prunus cerasus) group of cherry, because the present commercial varieties, Montmorency and Early Richmond, have been found fairly satisfactory for New York. The production of desirable duke cherries has also been given consideration, inasmuch as a productive high-quality duke would doubtless meet with favor among cherry producers and consumers.
In South Dakota, N. E. Hansen has been actively engaged since 1900 in breeding cherries suited to the west north central States. He has made many crosses, using the western sand cherry, Prunus besseyi, and other species of Prunus. The sweet cherries, P. avium, which are raised in the Eastern States and so extensively on the Pacific coast, are not hardy in the northern prairie States. The sour cherries, P. cerasus, are much hardier than the sweets, but they are not generally planted in this region. The Early Richmond and some other sour varieties are grown to a limited extent in the southern part of the State. Attempts to hybridize sweet and sour varieties with the native cherries have not been successful.
The following have been developed and introduced:
Select South Dakota sand cherries (Prunus besseyi): Sioux, Tomahawk, and S. Dak. No. 5.
Sand cherry Japanese plum: Sapa, Wachampa, Etopa, Eyami, Enopa, Ezaptan (sand cherry X Burbank Sultan plum), Opata, Owanka, Okiya, Cikana (sand cherry X Gold plum), Skuya, Wohanka, Wakapa (probably sand cherry X unknown Japanese plum).
Sand cherry X native plum: Cheresoto, Sansoto (sand cherry X De Soto plum).
Sand cherry X plum: Champa (sand cherry hybrid, a seedling of Sioux open- pollinated), Oka (seedling of Champa open-pollinated, probably with Japanese plum).
Sand cherry X Purple-leaf Persian plum: Stanapa (purple-leaved, semi- dwarf), Cistena (purple-leaved, dwarf).
Sand cherry X European apricot: Yuksa (sand cherry X New Large apricot).
At the Iowa Agricultural Experiment Station cherry-breeding work is being carried on by utilizing greenhouse-grown trees in the same way as in the work at this station with plums and peaches. The varieties consist of six species of Prunus, namely, avium, cerasus, besseyi, japonica Thunb., tomentosa, and capuli Cav. Trees of the following crosses are being grown in the nursery: Sapa plum (P. salicina Lindl. X P. besseyi) & Gold cherry (P. avium); P. serotina Ehrh. X P. capuli, and Zumbra X P. tomentosa. The object of this work is to obtain varieties of cherry hardy for Iowa and suitable for the Great Plains region.
At the North Dakota Agricultural Experiment Station, work on cherry breeding is carried on with objectives similar to those in South Dakota and Iowa. The Cooper sand cherry hybrid was introduced in 1935. Because of good quality of fruit and hardiness of tree, it is considered a substitute for the sweet cherry in that State.
In past years about 400 seedlings of open-pollinated Compass cherry [it's a plum, not a cherry. -ASC] have been grown. Only one seedling had horticultural value. About 500 chokecherry selections have been grown, and from this work variety improvement seems possible from the use of these cherries as parents. Fifty F1 seedlings were obtained from crosses made in 1926 of chokecherry X P. maackii Rupr. These seedlings are also of genetic interest and are under study. Seedlings of hardy Russian sorts and of open-pollinated Anoka are also being grown.
At the United States. Northern Great Plains Field Station at Mandan, N. Dak., sour and sweet varieties of cherries have been crossed with pin cherries (Prunus pensylvanica), western sand cherries (P. besseyi), Nanking cherries (P. tomentosa), and chokecherries. Seeds have been produced, but in most cases they failed to grow. One tree, a cross between Wragg and pin cherry, seems to be fairly drought-resistant and hardy. It blooms profusely but does not set fruit, probably because of self-unfruitfulness.
Several hundred pin cherry seedlings have borne fruit, but none has been good enough to select.
Several thousand western sand cherry seedlings have been grown. This hardy native fruit shows a decided and varied response to cultivation; there are marked variations in habit of growth and in size and quality of the fruit. A number of promising selections have been made and propagated for further testing. This fruit has also been used in crossing with plums and Nanking cherries. Some of the latter crosses are bearing, and both fruit and bush characteristics are intermediate between the western sand cherry and the Nanking cherry. Second-generation seedlings have been grown.
Large numbers of chokecherry seedlings have been grown, and while they show considerable variation, no real “chokeless”’ seedling, i. e., entirely nonastringent, has been found. A few of the best have been propagated on Prunus maackii stock for further testing.
Thousands of seedlings of the Nanking cherry have been fruited in the testing blocks. This fruit is not entirely hardy and tends to be a shy bearer. It has been used in crossing with standard varieties of cherries, the western sand cherry, and plums. The only viable seeds obtained were from the western sand cherry crosses.
In addition to the breeding work at the various institutions, extensive variety collections are located in a number of States where breeding material may be obtained. Some of these are the New York (State) Agricultural Experiment Station, the Ohio Agricultural Experiment Station at Wooster, the Colorado State College at Fort Collins, the Utah Agricultural Experiment Station at Ogden, the California Agricultural Experiment Station at Davis, and the Oregon Agricultural Experiment Station at Corvallis.
Cherry-breeding work at the Horticultural Experiment Station at Vineland, Ontario, Canada, was begun in 1915 and has been continued up to the present time. During the period 1915 to 1935, 2,587 seedlings were obtained and planted for study. These seedlings were from 27 variety crosses and 27 open pollinations. Sixteen have been selected as having horticultural value. Two hundred and eighty-one seedlings were obtained from crosses made in 1931, using Bing as the seed parent and Black Tartarian, Napoleon, and Victor as pollen parents, to obtain large, nonsplitting, black varieties. From crosses made in 1935, 1,040 seedlings have been obtained from Hedelfingen as seed parent and Black Tartarian, Bing, Victor, and Windsor as pollen parents, with the same object in view.
From the early cherry-breeding work the Victor variety was introduced in 1935. This variety was a selection from seed of open- pollinated Windsor, which was collected in 1916 by F. S. Reeves. It is a large, attractive white cherry. Approximately 4,000 trees of this variety have been planted in southern Ontario.
Gardner (14), in 1911, working in Oregon, failed to get a set of fruit from selfing 11 varieties of sweet cherry. In 1912 he attempted to intercross Bing, Lambert, and Napoleon. These varieties proved to be not only self-incompatible, but incompatible with each other, that is, they would not set fruit when selfed or when cross-pollinated among themselves. In orchards where Napoleon was interplanted with Republican, and away from the influence of other varieties, the Napoleon set a full crop. The same was true where Lambert and Bing were interplanted with Black Tartarian.
The results of early cherry pollination work from 1911 to 1913 in Oregon, as well as later work in that State and in California, show that all varieties of sweet cherry tested were self-incompatible. Republican, Black Tartarian, Coe, Early Purple, Elton, Knight, Major Francis, May Duke, Rockport, Waterhouse, Willamette, Windsor, and Wood were all self-incompatible. Republican and Black Tartarian were found to be good pollinizers for all the varieties. They, of course, do not set fruit when selfed.
Crane and Lawrence, working in England, have tested 33 varieties and found all of them to be self-incompatible. Important self- and cross-incompatible varieties were Black Eagle, Early Rivers, Knight (Knight’s Early Black), and Bedford Prolific, while among cross- compatible varieties were Black Tartarian, Schmidt, Wood, and Windsor.
For all practical purposes, therefore, we must consider all true sweet-cherry varieties of Prunus avium to be self-unfruitful, that is, no fruit will set from blossoms pollinated with their own pollen, since fertilization will not take place. The genetic explanation of self- incompatibility of style and pollen and its relation to failure of fruit to set has already been discussed in the section on plums.
Nearly all of the varieties of sweet cherries fail to set fruit when the flowers are pollinated with their own pollen. They are therefore said to be self-sterile. However, the pollen grains and egg cells of these varieties are functional, for the pollen will grow when placed on the stigma of another variety, and in like manner the egg cell will develop if fertilized with pollen of another variety. With most of the stone fruits fertilization is required before the fruit will develop, and a variety that does not set fruit because of the failure of its own pollen to effect fertilization of the flowers is said to be self-unfruitful.
Strictly speaking, sterility may be due to three causes (23): (1) Flowers may be sterile because of their morphological development. Failure of the anthers or pistils, or both, to develop, and failure to develop viable pollen or functional egg cells, may result in nonfruitfulness. It is recognized that such situations may be due to genetic causes. (2) Sterility may also be physiological. The pollen grains and egg cells may be normal; fertilization is effected, but the embryo does not grow because of certain nutritional disturbances. (3) Sterility may be due to incompatibility. In this case the pollen grains are normal and will develop in the style of other varieties and bring about fertilization of the ovules, but they will not function in the style of the flower of the same variety. It is this latter type of sterility that is most frequently encountered in the stone fruits. Nearly all of the sweet cherry varieties are self-unfruitful because of incompatibility. Varieties such as Napoleon, Windsor, and Black Tartarian will not set fruit when the flowers of any one of them are pollinated with its own pollen. If, however, Black Tartarian. pollen is applied to Napoleon or Windsor, a large percentage of the flowers will set fruit. Likewise, if Windsor pollen is applied to Napoleon or Black Tartarian, fruit- setting will occur.
The genetic basis of incompatibility has already been discussed in the section under plums.
In contrast to the sweet cherries, varieties of sour cherries are self- fertile, and the pollen of sour varieties will also effectively cause fruit-setting on sweets.
In duke cherries varying degrees of self-compatibility occur. Crane and Lawrence (10), working in England at the John Innes Horticultural Institution, have obtained the following percentage of set from selfing important duke varieties: 9 percent for Late Duke, 3 percent for Empress Eugenie, 1 percent for May Duke. Reine Hortense set no fruit. The results obtained from cross-pollinations between sweet, sour, and duke cherries have varied considerably. According to Crane and Lawrence, sweet varieties pollinated by sour varieties generally produce and mature fruits freely, but from reciprocal pollinations fruits are less freely formed. In a similar way fruit production is less when the dukes are pollinated by sweet varieties than when reciprocal pollinations are made.
We have little knowledge about the origin of our present cherry varieties. Three varieties produced by Thomas Andrew Knight, resulting from a cross of a sweet (bigarreau) X May Duke, were Waterloo, Knight (Knight’s Early Black), and Black Eagle, and the latter two would pass for sweet cherries. In pollination studies to determine the incompatibility of varieties, it has been observed, both in this country and in England, that individuals of the same variety appear to differ in their pollination requirements, and it is possible that distinct strains of such varieties or types as Black Tartarian or Napoleon have been propagated. Because of the fact that all varieties of Prunus avium are self-unfruitful it has been impossible to raise selfed progeny to study the inheritance of characters and determine genetic relationships. In studies made at the John Innes Horticultural Institution in England, Crane observed that in selfed families raised from varieties of P. cerasus, seedlings with P. avium characters frequently appeared, and in families raised from crosses between varieties of P. avium, occasional seedlings occurred which showed marked P. cerasus characters. Furthermore, seedlings in families raised from P. avium X cerasus resembled the dukes in many characters but not in all.
Cytological investigations of the cherries show the somatic chromosome number (27) in P. avium to be 16, and it is apparently diploid. In P. cerasus and the dukes the number is 32. Darlington (17), who has studied the chromosome behavior in a number of cultivated varieties of cherry, considers that P. cerasus is a true tetraploid, not derived simply from P. avium, but one possessing additional elements probably derived from P. fruticosa Pall., another tetraploid. All of the sweet cherries examined by Darlington had extra chromosomes beyond the diploid number. Irregularities occur in chromosome pairing, but it does not appear that there is any correlation between the actual chromosome number and the incompatibilities observed in sweet cherry varieties. Selfed seedlings of sour and duke varieties showed a chromosome number of 32. In crosses between the sour and dukes an examination of the progeny shows that the chromosome number is also 32. However, in crosses between dukes and sweets, and sours and sweets, the progeny showed the intermediate number 24 in some cases, as we might expect, and in others 32. The cultivated duke varieties appear to be tetraploids that have arisen from hybridization between the diploid sweet cherries and the tetraploid sours. In experimental studies, however, crosses between some tetraploid sours and diploid sweets have yielded seedlings with 24 chromosomes that presumably were triploids and proved to be highly sterile.
B. R. Nebel, at the New York Agricultural Experiment Station, has been studying the cytology of interspecific hybrids. From crosses between sour and sweet cherries, 22 triploid first-generation trees have been obtained, and these are fruiting on the station grounds. In attempting to backcross from these hybrids only 1 fruit was obtained in 700 pollinations. Open-pollinated seed was then used, and this gave nearly 50 second-generation seedlings. Upon cytological examination of this second-generation material there appeared to be a gradation downward in chromosome numbers through loss of some of the supernumerary chromosomes of the sour species. It is possible that the second-generation seedlings will be more fertile than the first- generation, and that backcrosses with firm-fleshed sweet cherries will give diploid dukes that are interfertile with sweet cherries, As already mentioned, if autopolyploidy could be induced, the first- generation triploids could be made fertile directly and much time could be saved.
Crane and Lawrence report from their studies of the inheritance of flesh color in sweet cherries that white is recessive to black. In crosses between white varieties only white was obtained. Bigarreau du Schrechen [Bigarreau de Schrecken -ASC]is considered homozygous for black, since in all crosses where this variety was used as a parent all of the progeny produce black fruits. Other black varieties, such as Early Rivers, Bedford Prolific, Black Tartarian types A and B, Late Black [So non-specific, I don't know which cultivar they are referring to. Searching The Cherries of New York for "Late Black" gives at least 4 candidates. -ASC], and Schmidt, are heterozygous for flesh color. It appears, however, that when the different shades of fruit color are considered, ranging from dark to white, through various pinks and reds, a number of genes may be involved in color inheritance.
Selfed sour cherry (morello) varieties with roundish oblate fruit gave seedlings that yielded occasional long fruits. Kentish Red, a variety with roundish oblate fruits, gave a progeny that yielded fruits of variable size and shape.
|State or country, institution and location|
|Workers actively engaged at present|
|California: Agricultural Experiment Station, Davis||A. A. Hendrickson, W. P. Tufts, G. L. Philp||W. P. Tufts, G. L. Philp, E. C. Hughes|
|Iowa: Agricultural Experiment Station, Ames||S.A. Beach||T. J. Maney|
|New York: Agricultural Experiment Station, Geneva||S. A. Beach||U.P. Hedrick, R. Wellington, G. H. Howe, B. R. Nebel|
|United States Northern Great Plains Field Station, Mandan||Max Pfaender||W. P. Baird|
|Agricultural Experiment Station, Fargo|
|A. F. Yeager|
|South Dakota: Agricultural Experiment Station, Brookings||N. E. Hansen||N. E. Hansen|
|Utah: Agricultural Experiment Station, Logan|
|F. M. Coe|
|Canada: Horticultural Experiment Station, Vineland, Ontario|
|F. E. Palmer, G. H. Dickson|