_The stem._
_Stem or trunk_: The unbranched main axis of the plant above ground.
_Branches or arms_: Main divisions of the trunk.
_Head_: The region from which branches arise.
_Old wood_: Parts of the vine older than one year.
_Canes_: Wood of the current season.
_Spurs_: Short pieces of the bases of canes; usually one or two nodes with a bud each.
_Renewal spurs_: Spurs left to bear canes the following year.
_Shoots_: Newly developed succulent stems with their leaves.
_Fruit-shoots_: Flower and fruit-bearing shoots.
_Wood-shoots_: Shoots which bear leaves only.
_Laterals_: Secondary shoots arising from main shoots.
_Water sprouts_: Shoots arising from advent.i.tious buds.
_Suckers_: Shoots arising from below ground.
_Nodes_: Joints in the stem from which leaves are or may be borne.
_Internodes_: The part between two nodes.
_Diaphragm_: The woody tissue which interrupts the pith at the node.
_Bloom_: The powdery coating on the cane.
_Tendril_: The coiled, thread-like organ by which the vine grasps an object and clings to it.
Species of grapes have very characteristic vines. A glance at a vine enables one to tell the European grape from any of the American grapes; so, also, one is able to distinguish most of the American species by the aspect of the vine. Many varieties of any species of grape are readily told by the size and habits of the plant. Size of vine is rather more variable than other gross characters because of the influence of environment, such as food, moisture, light, isolation and pests; yet, size in a plant or the parts of a plant is a very reliable character when proper allowances are made for environment.
The degree of hardiness is a very important diagnostic character in determining both species and varieties of grapes and very largely indicates their value for the vineyard. Thus, the varieties of the European grape are less hardy than the peach, while our American Labruscas and Vulpinas are as hardy as the apple. The range of varieties as to hardiness falls within that of the species, and cultivated varieties hardier than the wild grape are not found. Grapes are designated in descriptions of varieties and species as hardy, half-hardy and tender.
Habit of growth varies but little with changing conditions and is thus an important means of distinguishing species and varieties and not infrequently stamps the variety as fit or unfit for the vineyard.
Habit of growth gives aspect to the vine. Thus, a vine may be upright, drooping, horizontal, stocky, straggling, spreading, dense or open.
The vine may grow rapidly or slowly and may be long-lived or short-lived; the trunk may be short and stocky or long and slender.
These several characters largely determine whether a vine is manageable in the vineyard. Productiveness, age of bearing and regularity of bearing are distinctive characters with cultivated grapes. The care given the vine influences these characters; yet all are helpful in identifying species and varieties and all must be considered by the grape-grower.
Immunity and susceptibility to diseases and insects are most valuable diagnostic characters of species and varieties of grapes. Thus, species differ widely in resistance to phylloxera, the grape-louse, to the grape leaf-hopper, the flea-beetle, berry-moth, root-worm, powdery-mildew, downy-mildew, anthracnose and other insect and fungous troubles of this fruit.
The structure of the bark is an important distinguishing character for some species, but is of little importance in identifying the variety and has no economic value to the fruit-grower. In most species of grapes, the bark has distinct lenticels and on the old wood separates in long thin strips and fibers; but in two species from southeastern North America, the bark bears prominent lenticels and never shreds.
Smoothness, color and thickness are other attributes of the bark to be noted.
Canes of different species vary greatly in total length and in length of internodes. They vary also in size, in number and in color, while the shape in some species is quite distinctive, being in some round, in others angular and in still others flattened. The direction of growth in canes, whether sinuous, straight or zigzag, is an important character. Nodes and internodes are indicative characters in some species, being more or less prominent, angular or flattened, while the internodes are long or short.
The diaphragm distinguishes several species of grapes. The cane contains a large pith and this in most species is interrupted by woody tissue, forming a diaphragm at the nodes. In the Rotundifolia grapes the diaphragm is absent, while in several other American species it is very thin and in still others quite thick. The character of the diaphragm is best observed in year-old canes. In studying the diaphragm, notice should be taken also of the pith, which is very variable in size.
Young shoots of the grape offer a ready means of distinguishing species and varieties through their color and the amount and character of the p.u.b.escence. Shoots may be glabrous, p.u.b.escent or hairy and even spiny.
The tendril is one of the organs most used in determining species and varieties of grapes. In some species, as _V. Labrusca_, there is a tendril or an inflorescence opposite nearly every leaf, continuous tendrils. All other species have two leaves with a tendril opposite each and a third leaf without a tendril, intermittent tendrils. To study this organ it is necessary to have vigorous, healthy, typical canes. Tendrils may be long or short, stout or slender; simple, bifurcated or trifurcated; or smooth, p.u.b.escent or warty.
The number of inflorescences borne by species is an important character in some cases. All species, excepting _V. Labrusca_, average two inflorescences to a cane, but _V. Labrusca_ may bear from three to six inflorescences, each in the place of a tendril opposite the leaf.
_The bud._
_Bud_: An undeveloped shoot.
_Fruit-bud_: A bud in which a shoot bearing flowers originates.
_Wood-bud_: A bud in which a shoot bearing only leaves originates.
_Latent bud_: A bud which remains dormant for one or more seasons.
_Advent.i.tious bud_: A bud arising elsewhere than the normal position at a node.
_Eye_: A compound bud.
_Main bud_: The central bud of an eye.
_Secondary bud_: The lateral bud of an eye.
Buds of different species of grapes vary greatly in time of opening as they do somewhat in varieties, so that the time the buds begin to swell is a fine mark of distinction. The angle at which the bud stands out from the branch is of some value in determining species.
Differences in color, size, shape, position and amount of p.u.b.escence of buds must all be noted in describing grapes. The scales of the buds vary more or less in size and in thickness.
_The flower._
_Staminate_: Having stamens and not pistils; a male flower.
_Pistillate_: Having pistils and not stamens; a female flower.
_Dioecious_: Said when the stamens are on one plant and the pistils on another.
_Polygamous_: Said when flowers on a plant are in part perfect (having both stamens and pistils) while others are staminate or pistillate.
_Hermaphrodite_: Said of a flower having both stamens and pistils.
_Fertile_: Said of a flower capable of bearing seed without pollen from another flower.
_Sterile_: Said of a flower without or with abortive pistils.
_Perfect_: Said of a flower having both stamens and pistils.
_Imperfect_: Said of a flower wanting either stamens or pistils.
_Peduncle_: The stalk of a flower-cl.u.s.ter.
_Pedicel_: The stalk of each particular flower.
The time of bloom is an easy mark of distinction between several species of grapes and helps to distinguish varieties in a species as well. Most species of grapes bear fertile flowers on one vine and sterile flowers on another and are, therefore, polygamous-dioecious.
Sterile vines bear male flowers with abortive pistils so that, while they never produce fruits themselves, they usually a.s.sist in fertilizing others. Fertile flowers are capable of ripening fruits without cross-pollination. Vines with female flowers only are seldom found. In most species of the grape, plants with sterile flowers and those with complete flowers are found mixed in the wild state, but usually only the fertile plants have been selected for cultivation.
Plants raised from seeds of any of the species, however, furnish many sterile vines.
[Ill.u.s.tration: FIG. 53. The grape flower. I. Opening bud showing the way in which the cap becomes loosened at the base. II. Diagrammatic ill.u.s.tration of grape stamens.]
The degree of fertility of blossoms is also a fine mark of distinction in species and varieties of the grape. Fertile vines are of two kinds in most species. The flowers on one kind are perfect hermaphrodites, while in the other kind the stamens are smaller and shorter than the pistil and eventually bent down and curved under. The two kinds of stamens are shown in Figs. 53 and 54. These may be called imperfect hermaphrodites since they are seldom as fruitful as the perfect hermaphrodites unless fertilized from another plant. Examined with a microscope, it is found that self-sterile plants usually bear abortive pollen and that the percentage of abortive pollen grains varies greatly in different varieties. The upright or depressed stamen does not always indicate the condition of the pollen, since there are many instances in which upright stamens bear impotent pollen and occasionally the depressed stamens bear perfect pollen.
[Ill.u.s.tration: FIG. 54. Grape flowers. _Left_, upright stamens of Delaware; _right_, depressed stamens of Brighton.]
_The leaf._
_Blade_: The expanded portion of the leaf.
_Lobe_: The more or less rounded division of the leaf.
_Sinus_: The recess or bay between two lobes.
_Petiole_: The leaf-stalk.
_Petiolar sinus_: The sinus about the petiole.
_Basal sinuses_: The two sinuses toward the base of the blade.
_Lateral sinuses_: The two sinuses toward the apex of the blade.
The size, shape and color of the leaves are quite distinctive of species and more or less so of varieties, if allowances are made for variation due to environment. The lobing of leaves is a very uniform character in most species, some having lobes and others having entire leaves. The upper surface of the leaf in some species is smooth, glossy and shiny and in others is rough and dull. The lower surface shows similar variations and has, besides, varying amounts of p.u.b.escence, down and bloom. In some species the down resembles cobwebs. The number, size and shape of the lobes are important in distinguishing both varieties and species, as are also the petiolar, basal and lateral sinuses. As in most plants, the margins of the leaves, whether serrate, dentate or crenate, are often distinguishing characters. The petiole in different species varies from short to long and from stout to slender. Lastly, the time at which the leaves fall is often a good distinguishing mark.
_The fruit._
_Peduncle and pedicel_: Defined as in flower.