Читать книгу The Grapes of New York - U. P. Hedrick - Страница 17

1. V. bicolor 2. V. cordifolia 3. V. rotundifolia 4. V. doaniana 5. V. longii	6. V. labrusca 7. V. rupestris 8. V. riparia 9. V. vinifera 10. V. aestivalis
CANES OF SPECIES OF VITIS

Shortly after and partly coincident with Engelmann, Munson, of Texas, made valuable contributions to our knowledge of American grapes. Munson is, what none of his predecessors had been, a cultivator of grapes and a breeder of new varieties as well as a botanical student of the subject. The region in which he lived was comparatively new to botanists, and it was partly, perhaps, on this account that he raised the number of species from the thirteen given by Engelmann to twenty-five. At the present time it appears doubtful if all of these will ultimately be given specific rank. Many of them undoubtedly will, and others of them will be recognized at least as varieties. Munson is regarded to-day as the chief authority on grapes of the semi-arid and mountainous districts of the West and is one of the leading authorities on American viticulture.

The last man who has paid special attention to the grapes of North America is Bailey, of Cornell. In his latest classification he gives twenty-three species of American grapes. Bailey is the only American botanist of experience and recognized standing in general botany who has paid special attention to the grape. His monograph of the genus Vitis which, with some changes, has appeared successively in Gray’s Synoptical Flora, The Evolution of Our Native Fruits, and the Cyclopedia of American Horticulture, is the most complete work we have on this subject. With his permission we have followed his arrangement of species in The Grapes of New York.

With this brief history of the formation of the genus Vitis as it now stands we pass to a consideration of the botanical characters of Vitis.

From the time when botanists first commenced to work on the grape there has been a constant search for taxonomic characters for separating the various species clearly and distinctly. Many of the earlier descriptions, while they are correct so far as they go, do not mention enough characters to enable one to distinguish between similar species. It has been found that dependence upon the shape of the leaf, size of berry, size of plant, date of ripening, and similar characters, is very uncertain and unsatisfactory and that, while these characters are always mentioned in descriptions as indicating the intrinsic value of a species, they are of little value from a systematic standpoint. There are, however, several characters of Vitis which have great taxonomic importance.

One of the fundamental characters which determine a species is continuous or intermittent tendrils, first noticed by Professor A. Braun[120] of Berlin. Vitis labrusca, the common Fox grape, is peculiar in that there are tendrils, or an inflorescence, opposite nearly every leaf; this arrangement is known as continuous tendrils. All other species have two leaves with a tendril opposite each and a third leaf without a tendril; such species are said to have intermittent tendrils. Continuity of tendrils is a variable character and to ascertain which of the two forms is present it is necessary to have vigorous, healthy, typical canes. The lowest leaves of canes usually have no opposite tendrils. This character is shown in the color-plates of the several species.

A closely related character is that of the number of inflorescences borne by a species. All species excepting Vitis labrusca average two inflorescences to the cane but the last named species, at least in some of its subdivisions, may bear from three to six inflorescences, each of course in the place of a tendril opposite a leaf.

Professor Millardet of Bordeaux first called attention to the value of that part of the cane known as the diaphragm as a means of distinguishing species. The cane of the grape vine contains a large pith, and in most species this pith is interrupted by woody tissue at the joints; this woody tissue is the diaphragm. The presence or absence of the diaphragm and its thickness are of taxonomic value. In Rotundifolia, the southern Fox grape, the diaphragm is absent; in Riparia, the Riverbank grape, it is very thin; in Rupestris it is slightly thicker; while Cordifolia, Aestivalis, and Labrusca have thick diaphragms. This character is studied best in the year-old canes of the grape. The color-plate of canes shows the range in thickness of diaphragms as they occur in several species.

SEEDS OF SPECIES OF VITIS [Natural Size and Enlarged]

The time of flowering is of considerable value in distinguishing species. Unfortunately it requires live plants and a certain time of year in order that this character be noted. The first American species to flower is Riparia. Rupestris flowers shortly after; next, Labrusca; Aestivalis a little later, although the Lincecumii variety of Aestivalis blooms slightly before Labrusca; Cordifolia is very late in coming into bloom, and Cinerea still later. Vinifera, the European grape, blooms shortly after Labrusca. The cultivated offspring of all wild grapes retain the blooming characters of the species from which they are derived.

Other characters that have been found of great value are those connected with the seed. The ability to use the seed characters, however, cannot readily be acquired except by the use of an illustrated manual and some experience in selecting the seeds, as they are quite variable on the same plant. The weight of the seeds differs in different species, but varies so much inside the species that it is not of much value from a systematic standpoint. In general, it may be said that the Labruscas have the largest and heaviest seed of our American grapes; Riparia has the smallest seed, with Aestivalis occupying an intermediate position. The size of the seeds in Aestivalis, however, is more noticeable on account of the small size of the fruit. The color-plate illustrates the different characters to be found in grape seeds and a study of this plate with the technical descriptions of the several species will show how important seeds become in classifying grapes.

Attention is called to the characters given by Bartram as distinguishing the European from the American species. The first difference that he mentions is in the shape of the fruit, that of the Vinifera being more or less oval and that of American species roundish or oblate. Recent technical descriptions of our American species give the fruit as spherical where the shape is mentioned at all. On the other hand it is known that most of the cultivated varieties of European grapes are oval. Does this mean that all of our cultivated American varieties which show oval berries, such as Isabella, Catawba, and others, contain Vinifera blood? It could not be said without careful study that this is true but it is certainly worthy of consideration. This point seems to have escaped the attention of our later-day botanists.

The sexual status of the grape has always been a source of misunderstanding. The earlier botanists spoke of American vines as dioecious, that is, bearing staminate and pistillate flowers on separate individuals. In this, as was noted on page 98, they were corrected by Bartram, in so far as American species were concerned, he stating that the vines of America were polygamous (showing staminate and hermaphrodite plants). Bartram did not presume to speak as to the sex of the flowers of the Old World grape. Later it was determined that the cultivated varieties of Europe were always hermaphrodite and that staminate forms were unknown. Engelmann[121] explains this so well and with such apparent satisfaction that we cannot do better than quote him here. “All the true Grape-vines bear fertile flowers on one stock and sterile flowers on another separate stock, and are therefore called polygamous, or, not quite correctly, dioecious. The sterile plants do bear male flowers with abortive pistils, so that while they never produce fruit themselves, they may assist in fertilizing the others; the fertile flowers, however, are hermaphrodites containing both organs—stamens and pistils—and are capable of ripening fruit without the assistance of the male plants. Real female flowers without any stamens do not seem ever to have been observed. Both forms, the male and the hermaphrodite, or if preferred those with sterile and those with complete flowers, are found mixed in their native localities of the wild plants, but of course only the fertile plants have been selected for cultivation, and thus it happens that to the cultivator only these are known; and as the Grape-vine of the Old World has been in cultivation for thousands of years, it has resulted that this hermaphrodite character of its flowers has been mistaken for a botanical peculiarity, by which it was to be distinguished, not only from our American Grape-vines, but also from the wild grapes of the old world. But plants raised from the seeds of this as well as any other true Grape-vine, generally furnish as many sterile as fertile specimens, while those propagated by layering or by cuttings, of course, only continue the individual character of the mother-plant or stock.” The accompanying plate shows various forms of grape flowers.

FLOWERS OF VITIS

He further says in a foot-note: “These fertile plants, however, are of two kinds; some are perfect hermaphrodites, with long and straight stamens around the pistil, the others bear smaller stamens, shorter than the pistil which soon bend downward and curve under it; these may be called imperfect hermaphrodites, approaching females, and they do not seem to be as fruitful as the perfect hermaphrodites, unless otherwise fertilized.”

Beach[122] tested many of our cultivated varieties by sacking the clusters at blooming time and thus determined their capacity to fertilize themselves. From the data thus secured he divides them into four classes: 1st. Those that are able to fertilize themselves so that the clusters are perfect or varying from perfect to somewhat loose. 2d. Those in which the clusters are marketable, varying from moderately compact to loose. 3d. Clusters so loose as to be unmarketable. 4th. Those which are self-sterile or showing no fruit on covered clusters. Of 169 varieties tested, he found 38 belonging to the first class, 66 to the second class, 28 to the third, and 37 to the fourth.

Later it was found that the reason why certain varieties were self-sterile was on account of impotent and abortive pollen, the percentage of abortive pollen grains varying with different varieties and this percentage determining the degree of self-sterility. The upright or depressed stamen is not an invariable criterion of the condition of the pollen although it is usually. There are a few instances in which upright stamens bear impotent pollen but these are very exceptional. Munson made similar tests of vines of twenty-two[123] American species of vines secured from their habitats. In every case he found that they showed only two forms, the staminate vines and the self-sterile hermaphrodite, no perfect hermaphrodites being found. While of some of the species the number of vines tested was a half dozen or less, in most instances many vines were tested from different places. This is particularly interesting in that it becomes a puzzle as to where our perfectly hermaphrodite cultivated forms could have come from if such forms are not present in the wild vines of our woods and prairies.

The structure of the bark is an important distinguishing character for some species; in particular as to whether it peels off and whether in large flakes or in narrow strips or shreds. So, too, the color of the bark is often of taxonomic importance. The form and color of the leaves are often considered, but these characters are variable and may be misleading. The lobing of leaves is a fairly uniform character in most species, some having lobed and others having entire leaves. As to color and texture, the upper surface of the leaf in some species is smooth, glossy and shining and in others rough and dull with varying shades of green. The lower surfaces show similar variations with the addition of varying conditions of pubescence and down or even of cobwebs. In young seedlings the shape and surfaces of the leaves are apt to be quite different from those on the old plants, a character of systematic importance with some species. The flower, as compared with this organ in other genera, is of little importance in distinguishing the species of Vitis, there being an unusual similarity in the structure and appearance of the flowers of the several species.

The number of species of Vitis is very uncertain; as, indeed, is their habitat, except that they are generally confined to the temperate or subtropical regions. Some writers give the number as less than fifty but in all territories the number seems to depend on the thoroughness with which the region has been worked over botanically, and also on the judgment of the botanist doing the work. Gray recognized four species as being indigenous to America. Engelmann in his latest publication (Bushberg Catalogue, 1883), thirteen, while Munson gives twenty-five. Bailey in Gray’s Synoptical Flora, gives twenty-three species. Planchon (in 1887) gives twenty-eight species for the world. Seventeen of these are credited to America, ten to Asia, and one, the Vinifera, of unknown nativity. All of these lists, however, are known to be incomplete. Bessey[124] says that the grape is not native to the southern hemisphere, and Planchon credits none to any section south of the equator. Bailey credits two to Australia in a work not intended to cover more than those of American interest. And a correspondent[125] from that continent writes us giving a list of nineteen named and botanically described species indigenous to Australia. The number of species of grapes in the world depends upon the arbitrary limits set for a species and our knowledge of the genus is yet too meager to set these limits with certainty.