All that is known of the history and habitat of this species is that it came from China in 1867 having been sent to the Paris Museum of Natural History by Eugene Simon, a French consul in China. The spontaneous form has not as yet been found. The general aspect of the tree is more that of the peach than the plum and the drupes are as much like apricots or nectarines as plums but when all characters are considered the fruit can better be classed with the plums than with any of the other stone-fruits named.

Prunus simonii has been widely grown in America both for its fruits and as an ornamental, but it cannot be said that it has become popular for either purpose and only one variety of the species is now under cultivation. As a food product the plums lack palatability and as ornamentals the trees are subject to too many pests. Prunus simonii has been successfully hybridized with Prunus triflora and as secondary crosses its blood has been mingled with that of some of the native species as well. Most of its hybrid offspring have more value than the parent, nearly all of them lacking its disagreeable taste. According to an article published in Revue Horticole[110] a new form of the Prunus simonii was produced in 1890 from a bud sport, the fruit of which is elongated, a little cordate, slightly unequal, and grooved on one side. So far as can be learned this sport has no very decided merits as a horticultural plant.

10. PRUNUS AMERICANA Marshall

As Prunus americana is more carefully studied throughout the great territory it inhabits, undoubtedly one or more sub-species will be described. The plums of this species in the Mississippi Valley are distinguished from the eastern and typical form by fruits having a length greater than the diameter, by a somewhat different aspect of tree and by flatter seeds which are usually conspicuously longer than broad. All of the cultivated varieties come from the western form. The plant of Prunus americana in the dry plain regions in Kansas and Nebraska becomes shrubby in character while on the alluvial bottom lands along the streams in this region it retains the character of a tree. In the southern limit of its range, the leaves of this species are more or less pubescent on the lower surface. As the species occurs throughout western New Mexico, Colorado, Utah, Wyoming, Montana and Manitoba, it differs enough, possibly, from the eastern types to be considered a sub-species, having a wholly different aspect of tree, silvery and somewhat scurfy twigs, smaller, thinner and lighter colored leaves and smaller fruits with more roundish stones.

Prunus americana is the predominating native plum. It is the most widely distributed, is most abundant in individual specimens and has yielded the largest number of horticultural varieties of any of the native species. Because of its prominence and comparatively high degree of permanency of characters it may well be considered the type from which has sprung not only its botanical varieties but several other of the American species. Its variability, too, is shown in its many diverse horticultural varieties, and of its adaptability it may be said that it flourishes on nearly all soils and exposures, and is found wild or cultivated from Maine to Florida and northward from Mexico along the eastern slope of the Rocky Mountains well into Canada. The species was well named by Marshall “Americana.”

This plum has not played nearly as important a part in the pomology of America as its merits would warrant. It seems to have made an impression almost from the first upon the Europeans who settled America, for it is mentioned in nearly all the early records of the food products of the newly found land, yet its cultivation can hardly be said to have begun until the last half of the Nineteenth Century. But the early descriptions of this and other native plums by the colonial explorers, naturalists and botanists, show but little interest in these fruits as subjects for cultivation, and seem to contain almost no prophecies as to the possible development of a new orchard plant from them. It is probable that the Damsons, which were early introduced in America, and the Domesticas, which came at least before the Revolution, proved so adaptable to the part of the New World in which the colonies were planted that this, even though the best of the wild plums, offered small reward in comparison.

It is certain, however, that from the very first, Americana plums were much used by the early settlers as wild fruits, for the histories of all the colonies and states in which plums are found contain innumerable references to wild plums, usually with some expression showing that they were considered makeshifts until the European plums could be grown. Long before white men came to America the possessors of the continent knew and esteemed these fruits of the woods. According to some of the early writers wild plums of this species, since found where the Americanas are dominant, were planted and rudely cultivated by the natives.[111] It is likely, however, that these Indian orchards were more often the result of seeds dropped about camping places and towns rather than regularly planted orchards. It is not improbable that the wide distribution of this species in the Mississippi Valley and the country about and beyond the Great Lakes is due somewhat to the hand of the Indian, of the voyageur and of the missionary of the French regime.

The common names under which this plum passes in the states where it is found as a wild fruit are indicative of the knowledge possessed of it by the people. The Americana is nearly always the wild plum of eastern America. It shares with several other species the names in various parts of the country of Red Plum, Yellow Plum, the Horse and the Hog Plum. In Iowa this is most often the “native plum;” in Indiana it is the Goose plum; in Georgia, the August plum, while in the states bordering on the Gulf it is often called the Sloe.

The domestication of Americana plums is due to the fact that the plums of Europe will not thrive in the Mississippi Valley, the prairie states, nor, for the most part, in the South. The European species are tender both to cold and heat in these regions and they are attacked by those scourges of plum culture, black-knot, leaf-blight and curculio. If, then, the people in the West and South were to have plums at hand when wanted, the wild species had to be brought under cultivation. Where the two will grow side by side it is doubtful if any would choose to grow the Americanas in preference to the Europeans or even for the sake of variety.

The Americana plum was introduced into European gardens at an early date, for references to it are found in the pomological works of the Eighteenth Century, Duhamel having described it in his great work on pomology in 1768, under the name Prunier de Virginie, and later Poiteau[112] gives a very good description of it under the name Prune de la Gallissioniere. Just how much earlier than these dates it was taken to the Old World cannot be said, but seeds of it are likely to have been taken there by some of the returning explorers of early colonial times. The important fact is that as a cultivated fruit it has made absolutely no headway in competition in Europe with the plums of that continent though it is to be found not infrequently as an ornamental.

The domestication of these plums began less than a century ago, not through direct efforts in breeding them but as the result of the selection of the best of the wild or chance trees found in many widely separated localities. It would be most interesting to follow in detail the introduction of variety after variety of this species into cultivation, giving full credit to the men, many of them pioneers in newly settled countries, through whose efforts the amelioration of the species was begun. But space forbids, and the reader who desires to trace more fully the history and the evolution of these plums must put together the histories of the two or three hundred varieties of Americanas described in the chapters on varieties.

Are the Americanas to compete with the Domesticas, Insititias and Trifloras where all may be grown? It is very doubtful or at least not soon. The Old World plums are so superior, speaking generally, in size, appearance, and flavor, the qualities which appeal to those who eat plums, that the native varieties stand small chance for popular favor. Their place in pomology must long remain the region where the older and more highly developed groups of plums cannot be grown. Though there are now many times more of the Americana plums under cultivation than of the recently introduced Trifloras, the latter are more popular and are likely to remain so in localities where both can be grown.

The range of Prunus americana is seemingly increasing, making it almost impossible to give its present limits. The boundary line of its northern range passes through central New York to central Michigan, southern Wisconsin, Minnesota and South Dakota extending northwestward to Manitoba and reaching its western limit in Utah. It occurs locally southward through Colorado to northern New Mexico. It is rare in Oklahoma and does not occur in Texas, but is represented in Missouri by a pubescent form. East of the Mississippi River the typical species occurs in all of the states from central New York southward to northern Florida. In this great territory it is found in many diverse soils and exposures but responding in all to good soil and congenial environment. In the wild state the Americana plums are most often found along the borders of streams and swamps or in bottom lands where moisture abounds. Sometimes they are found in swamps which may be submerged a part of the year. In spite of a predilection for moist lands, however, the wild plants are not infrequently found on comparatively dry uplands, seeming to prefer soils containing considerable lime. The wild trees are usually found in thickets, often of considerable extent.

Under cultivation the range is even greater than for the wild plant. It is only in localities of extreme heat and cold, humidity or aridness, that some of the many Americanas cannot be made to grow under conditions at all favorable for orchards of any of the temperate fruits. So, too, varieties may be found for nearly all soils which permit of cultivation. This freedom from local attachments is one of the chief assets of the species.

The Americana tree is commonly small, often but a bush, and usually with a thick, thorny top. Generally the head attains a height of about fifteen or eighteen feet and sometimes it rises to twenty-five or thirty feet, spreading into many rigid branches which are often pendulous at the extremities. The species may almost always be told by the rough, shaggy, grayish bark, the large, thin, persistent plates of which give a very characteristic shagginess. In the spring the tree is covered with umbelliferous masses of pure white flowers and both at this season and later with its ample foliage or showy fruit, the plant is very ornamental. The leaves are large, oval or obovate, thin, dull and veiny, with very jagged margins.

The fruit is reddish or yellowish or a blending of the two with the red varieties predominating. Often the color is more nearly orange than red or yellow—in fact pure yellow fruits cannot be found. Wild or cultivated the fruits of the Americana plums vary greatly in season, size, shape and flavor. In the orchard the period of maturity covers a range of several weeks, beginning in New York in August and ending in October; in the wild, trees in the same thicket may vary as much as three weeks in ripening their fruit. The size of the cultivated sorts is from that of a Damson to that of some of the Gages, the shape being roundish-oval, or quite oval, sometimes oblique and sometimes truncate at one or both ends and often more or less compressed. The wild fruits usually have a pleasant flavor and this is much improved under cultivation so that when fully ripe the flesh of some sorts is sweet and luscious, hardly surpassed, if the skin be rejected, by the best Domesticas. The skin is usually thick, coriaceous, acerb or astringent, and altogether very unpleasant, making with the tenaciously clinging stones the chief defects of these fruits. In some varieties skin and stones are far less objectionable than in others.

The trees of the varieties we have as yet are not very manageable in the orchard. They make a very slow growth and are hard to control, producing at maturity many leaning trunks which are often crooked, as are also the branches which, with the unkempt heads, give an impression of waywardness and wildness. Nearly all of the varieties over-bear and unless thinned the fruits are so small as to be hardly worth harvesting; not infrequently trees die from over-bearing. A few varieties are unfruitful but usually because of defective pollination. Nearly all sucker badly on their own roots, and except in cold regions should be grown on other stocks. In general there are fewer pests to combat with these than with the European plums but yet they are far from being exempt and require on the grounds of this Station quite as much spraying as do other plums.

Waugh, who has given the subject much study, claims that the Americanas are not very strong sexually,[113] chiefly because of defective reproductive organs. He found in extensive examinations that 21.2 per ct. of the pistils were defective, ranging from nothing in some varieties to 100 per ct. in others. More seldom the anthers were defective and the flowers were sometimes proterandrous (the pollen maturing before the pistil is ready to receive it), and that they were rather frequently proterogynous (the pistils receptive before the pollen is mature). Waugh holds that in planting these plums, provision should be made for cross-pollination, and recommends as sorts most suitable for inter-planting for this purpose, other varieties of the same species.

Plant-breeders have not found that this species hybridizes as readily as most of the other cultivated native plums. This is chiefly due to a seeming lack of affinity for other species. Nevertheless there are numerous Americana hybrids, and it is likely that as the high quality of the fruit and the hardiness of the trees become better known they will be used much more for hybridizing.

The Americana plums are all hardy and some of the varieties can be grown as far north as general agriculture is practiced. These, with the Nigras, will probably always be the chief groups for dry, cold regions between the Great Lakes and the Rocky Mountains. They may also be relied upon in the colder parts of New York and New England. The flower-buds as well as the trees are hardy, having been known to withstand a temperature of forty degrees below zero. Goff[114] reports that in the winter of 1896-7 the flower-buds of Domestica varieties on the grounds of the Wisconsin Experiment Station were almost totally destroyed though the minimum temperature recorded was only twenty-three degrees below zero, but the flower-buds of Americana varieties were not at all injured. Since the blossoms open comparatively late there is less damage from spring frosts in this than in most other species even of the natives.

The number of varieties of Americana plums is a testimonial to the merits of the species. There are about 260 varieties of them more or less disseminated. There are many divergent types of these and since all are far from what may be eventually expected from the species the number of varieties will undoubtedly greatly increase and in still other directions. In the meantime the great majority have fallen by the wayside. The weeding-out process seems to be in this case the chief agent of progression. A fault with the varieties now before the public is that many of them are so similar that a difference can hardly be detected. The elimination of the great majority of the varieties of this species now in the catalogs and a much more judicious selection of varieties for future dissemination would relieve pomology of the burden it now carries in the numerous sorts of Americanas.

PRUNUS AMERICANA MOLLIS[115] Torrey and Gray

Prunus americana mollis is a western and southwestern form of Prunus americana, the sub-species being distinguished from the species by the amount and character of the pubescence on the leaves and shoots. The leaves, petioles and shoots of this plum are soft-pubescent, almost tomentose, the tomentum being pale in color and usually very dense; the calyx-lobes are pubescent on both sides and the pedicels are appressed and densely pubescent. According to Bailey, there is a form of this sub-species “with flowers as completely double as those of St. Peter’s wreath, or similar spireas.” This double-flowering plum we have not seen.

It is impossible to give the range of Prunus americana mollis as the woolly-leaved plum of the west gradually passes into the smooth-leaved species of the east and the two forms are not infrequently mixed in the South and Southwest; or possibly it would be better to say that they run into each other though the extreme forms are sufficiently distinct as to be readily mistaken for separate species. It can only be said that it is to be found in the greatest abundance in the region extending from southern Iowa through Missouri. Only two varieties of this plum, Wolf and Van Buren, are in general cultivation, both of which originated in Iowa. In neither fruit nor tree-characters do these differ greatly from the Americana plums.

A plum with pubescent leaves belonging to the Americana series known locally as the Big Tree plum, occurs from western Tennessee, south-westward through the extreme southern portion of Missouri, through Arkansas, southern Oklahoma, extending westward in central Texas, at least, as far as the Colorado River and reaching its southwestern limit in northern Mexico. From specimens of this plum in several herbaria and from studies made of it in the field by W. F. Wight of the United States Department of Agriculture, it would seem that this plum is a distinct species, its chief distinguishing character being the great size attained by the tree. So far as it is known the Big Tree has no cultivated forms unless it be Bilona, supposed to be a hybrid between this species and Prunus triflora, now growing on the grounds of F. T. Ramsey, Austin, Texas.

11. PRUNUS HORTULANA Bailey[116]

Prunus hortulana as established by Bailey, to quote a part of the original description, “includes a large class of plums represented by Golden Beauty, Cumberland, Garfield, Sucker State, Honey Drop, probably Wild Goose and others.” Unfortunately Bailey later added[117] a number of other plums to the group which the above varieties and some ten or fifteen others comprise, the additions in themselves constituting at least three somewhat distinct groups, and then to account for this omnibus species called it a “brood of natural hybrids.” Waugh supports Bailey’s conclusions[118] and divides the species into four groups of hybrids—the Miner group, the Wild Goose group and the Schley or Clifford group. These, Waugh says, “form an unbroken series from Prunus americana to Prunus angustifolia.” The fourth of Waugh’s groups, “comparatively distinct from the others, is made up of such varieties as Wayland, Moreman, Golden Beauty, Reed, Leptune, Kanawha and others.” These plums he designated as the “Wayland group.” This disposition of the plums under consideration leaves Prunus hortulana as the name of only a rather loosely related lot of cultivated varieties. It is probable that neither Bailey nor Waugh, had they seen the material now to be had, would have left the species as they did.

There is an abundance of herbarium material to show that Prunus hortulana as originally described by Bailey, with the varieties named as the type, leaving out Wild Goose, which is but doubtfully included, and as represented by Waugh’s “Wayland group,” is to be found wild in Illinois, western Kentucky, western Tennessee, Missouri and northern Arkansas, Oklahoma and southeastern Kansas. The writer has not seen material from states adjoining those named but the species is probably more widely spread than the range given indicates. Further, the cultivated varieties named by Bailey as members of his species, to which should be added at least American Golden, Benson, Columbia, Crimson Beauty, Dunlap, Kanawha, Leptune, Moreman, Reed, Wayland and World Beater, are so similar in all their characters and constitute a group so distinct from any other species that it is impossible to place them otherwise than in a distinct species. A group of hybrids could hardly be so uniform, and, moreover, these varieties contain characters, like late blooming, late fruiting, color, texture and flavor of fruit, leaf-serrations and deposits of red cork-cells in the bark, which other native species do not have, thereby shutting out the probability of the hybridity theory in which the supposed parents are Prunus americana and Prunus angustifolia. Lastly, and most convincing, varieties of the species come true to seed, which of course, would not be the case were these plums hybrids. From seed borne in 1893 this Station has had six seedlings of World Beater and four of Golden Beauty attain the age of sixteen years with more or less fruit for thirteen successive years. The seedlings could hardly be distinguished from the parents and showed no pronounced characters of either of the species of which Prunus hortulana has been supposed to be the hybrid offspring.

Of the sixteen varieties named as certainly belonging to this species, ten came from wild plants or seeds. Two of the remainder came from planted seeds and the origin of the remaining four is not known. One of the varieties from the wild, Golden Beauty, if its history as commonly given is correct, came from the Colorado River in western Texas. The Golden Beauty now under cultivation almost certainly belongs to Prunus hortulana, though it differs somewhat from other varieties of the group, but how it could have come from the wild in western Texas, so far from the usual range of the species, is at present unexplainable. This and other idiosyncrasies of distribution were reasons given by Bailey and Waugh for calling this species a group of hybrids. A careful study of localities from which all other Hortulana varieties than Golden Beauty have come shows them to be well within the range of Prunus hortulana. The fact that Golden Beauty is perfectly hardy at Geneva, and according to Waugh fairly so at Burlington, Vermont, suggests either that what we have as Golden Beauty did not originate in south central Texas or that the plant from which it came must have been introduced there within comparatively recent times.

Prunus hortulana gives to American pomology a very distinct and valuable group of plums which fortunately are adapted to a wide range of conditions, especially of climate. The Hortulanas are particularly well suited to the Mississippi Valley and southern states and fruit well as far north and east as New York. The product of Wayland, Kanawha and Golden Beauty, best known of the plums under discussion, is especially suitable for preserves, spicing and jelly, being unsurpassed by any other of our plums excepting the Damsons for these purposes. They are quite too acid and the flesh clings too tenaciously to the stone for dessert plums or even for ordinary culinary purposes. These plums, having firm flesh and tough skins, ship and keep splendidly and since they are the latest of the native plums in ripening, extend the season for this fruit very materially. The Wayland-like plums make very good stocks upon which may be grafted not only the varieties of the same species but those of the other native species as well. A point of especial merit with these plums as stocks is that they do not sucker as do most other species. Unfortunately they cannot be propagated from cuttings and the difficulty of obtaining seed at present precludes their use very generally. The Hortulana plums hybridize freely with other native species and their hybrids are such as to commend this species very highly to plum-breeders for hybridization.

Waugh[119] has given the name Prunus hortulana robusta to a group of hybrid plums of which Prunus triflora and various native varieties are the parents. For most part these hybrids resemble the American more than the Asiatic parent. Since these plums differ so among themselves it is doubtful if more can be said as to the characters of Waugh’s group than to mention the above resemblance. Some thirty or more varieties fall into this group of which America, Golden, Juicy, Ruby, Waugh and Gonzales are chief.

PRUNUS HORTULANA MINERI Bailey

It is impossible from present knowledge to say certainly whether the Miner-like plums put by Bailey into a botanical sub-division of Prunus hortulana are extreme variations of the species or, as Bailey in his last accounts and Waugh at all times have supposed, are hybrids between Prunus hortulana and Prunus americana. It is certain that all of these plums are intermediate in some characters between the two species named; neither botanists nor pomologists can agree as to whether certain varieties belong to the one or the other botanical division. There are, however, in several herbaria, specimens from the wild, and from different localities, that indicate that there is a distinct plum toward the northern limit of the range of Prunus hortulana which, if a natural hybrid, is of so ancient hybridity that the plants now come measurably true to type. The chief representatives of the Miner-like plums under cultivation, as Miner, Forest Rose, Prairie Flower and Clinton, are so like these wild plums as to lead the writer to believe that Bailey’s botanical sub-division is justified and is worth continuing even though a considerable number of the varieties now put with Miner, most of which have originated under cultivation, are hybrids and that the wild plums may have come from natural hybrids of more or less remote time.

The sub-species differs from the species in having shorter, stiffer, less graceful branches; leaves smaller, thicker, rougher and of a bluish-green cast; the blossoms of the two are much the same but those of the sub-species open a few days earlier; the fruits of the sub-species are larger than those of the species, lighter red, have more bloom, are less firm in texture, ripen earlier, yet later than those of any other species, and are quite different in flavor, having more nearly the taste of the fruit of Prunus americana; the stones, as well as the fruits, are very different, being in the sub-species larger, broader, flatter, smoother and less pointed. The differences in fruit and stone, and to some extent in the leaves, can be seen if the color-plates of Forest Rose and Wayland be compared.

In fruit-growing, the Miner-like plums behave in general much like the Americana plums. In some respects the fruits are an improvement upon those of the Americana varieties. For example the skin in the Miner-like varieties is usually less tough; is brighter in color and the flavor, in most cases, is a little better. These plums seem to be nearly or quite as hardy as the Americanas and are adapted to quite as wide a range of soils. Presumably they have the same value as stocks, though they seem not to have been tried for this purpose and they should have equal value at least in plant-breeding. The trees of the Miner-like plums are rather more amenable to domestication than those of Prunus americana having as orchard plants straighter trunks, more symmetrical and less unkempt tops and making larger trees. The fruits ripen so late as to make the varieties of this group especially valuable in prolonging the season for plums in regions where native varieties are grown exclusively. About twenty varieties of this sub-species are under cultivation.

12. PRUNUS NIGRA Aiton

It is possible that a group of Nigras, those occurring in western Wisconsin and Minnesota and about the upper extremity of Lake Superior ought to be described as a sub-species since they have a somewhat different aspect of tree and the fruits are a darker shade of red and show more bloom; the calyx is more pubescent and the calyx-glands more sessile. The differences in environment may change these characters, as indicated above, but they seem very constant in the cultivated varieties of the groups, most of which come from the west, and therefore sufficient to segregate this form from the species.

The Nigra is the wild plum of Canada. Its most common name, “Canada Plum,” is distinctly applicable and is here supplanted by “Nigra” only for the sake of uniformity. This is undoubtedly the dried plum which Jacques Cartier saw in the canoes of Indians, in his first voyage of discovery up the St. Lawrence in 1534.[120] These primitive prunes, Cartier says, the Indians called “honesta.” In his second voyage, the next year, he enumerates among other fruits the plum, “prunier,” growing on the “Ysle de Bacchus,” named from its “Vignes.” Dried plums, we learn from many later accounts, were a staple article of the winter diet of the savages. That the Indian tended the trees is probable, for the early explorers often record that plantations of plums were found about the aboriginal towns. Undoubtedly the range of this species was greatly extended by the Indians.

The Nigra is the most northern of the American plums, being an inhabitant of a region bounded on the north by a line passing from southern New Foundland westward to the Strait of Mackinac and thence southward to Lansing, Michigan. Its southern boundary can be but illy defined, but the species is common in New England, northern New York, where it is sometimes cultivated about houses, and westward at least as far as the eastern shore of Lake Michigan for the species, while the western form reaches the western boundary of Minnesota at least. Small[121] reports it as far south in the Appalachian System as northern Georgia. In the great region outlined above it is distributed in more or less scattered localities, being found usually in the valleys of rivers and streams, though often on high lands and in open woods, in the last locations preferring a limestone formation.

There has been much discussion as to whether Prunus nigra should be given specific rank or be united with Prunus americana, either as a part of that species or as a botanical variety of it. Until the revival by Sargent in 1892 of the name given the group by Aiton in 1789, the botanists of the latter half of the Nineteenth Century had for most part described the two groups under Prunus americana. Since Sargent’s re-establishment of the species, botanists have very generally regarded it as worthy of the rank. Bailey and Waugh, the leading horticultural authorities on plums, however, consider Nigra as but a botanical variety of Americana. The taxonomic characters of Prunus nigra seem to the writers of The Plums of New York to be as distinct as those of several other of the native species of Prunus, and since the species now is generally recognized by botanists, we have considered it in this work as distinct from Prunus americana.

The two species may usually be distinguished by the following differences: (1) The general aspect of the trees is very different. The tree of Americana is larger, the top is more spreading, and its branches longer, with more twigs, more slender and more pendulous. The bark on the trunk is lighter-colored and much more shaggy than in Nigra. (2) The wood of Nigra is tougher and the trees do not break as readily as those of Americana. The wood is also lighter in color. (3) The leaves of Nigra are larger, broader and the serrations are not so deeply incised nor so often double. Very distinct and very constant are the glands to be found on the teeth of the serrations on the young leaves of Nigra. These glands disappear as the leaves grow older, leaving a calloused point which makes the serrations of Nigra rounded, while those of Americana are acute, this being one of the most constant differences. (4) The flowers of Nigra appear several days earlier, are larger and are more pink than those of Americana. (5) The calyx-lobes of Nigra are glandular and the leaf-stalks are biglandular, characters usually not found in Americana. The calyx in all its parts is glabrous or at least far less pubescent than in Americana and if present the hairs are short and stiff, whereas in Americana the pubescence is soft. (6) The fruit of Nigra ripens earlier and is darker in color with less bloom and is more oblong than that of Americana. The skin of the plum is thinner and is not so objectionable either cooked or eaten out of hand. (7) The stone of Nigra is usually larger, flatter and more strongly crested. The characters of the two species vary much in different individuals and there are many intermediate forms but the differences seem as constant as between other species of this variable genus.

The Nigra plums are important horticulturally because they can be grown in somewhat colder regions than the Americanas. They not only endure more cold than the last named group, but their tough wood enables them to stand better the weight of snows and the stress of winds. Their earliness, too, prolongs the season for this type of fruit and in regions where the season is short they may be grown with more certainty than other groups. In habits and characters other than those named they are so like the Americana as to need no further discussion. About forty varieties of this species are under cultivation.

13. PRUNUS ALLEGHANIENSIS Porter