CHAPTER XIII 



BOTANY OF THE GRAPE 



The botany of the grape is simple. The 

 organs of vine and fruit are easily recognized, 

 and there are no other pomological plants with 

 which the species of Vitis can be confused. 

 While there are several cultivated species, each 

 constitutes a natural group so distinct that the 

 grower can hardly mistake one for another, 

 if he has knowledge of the structure and habits 

 of growth of the botanical groups of grapes. 

 While it is less easy to distinguish horticultural 

 varieties, this is not so difficult a task as with 

 tree-, bush-, or bramble-fruits, since the dif- 

 ferences in structure and habits are greater. 

 Attention must now be called to the differences 

 in organs on which botanical and horticultural 

 classifications are founded. 



The grape plant. 



The structure of the root is important in 

 distinguishing species. The roots of some 

 species of the grape are soft and succulent, as 

 those of V. vinijera, while the same organs in 

 other species, as in most American grapes, are 

 hard and fibrous. They may also be few or 

 numerous, deep or shallow, spreading or re- 

 stricted, fibrous or non-fibrous. 



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 in- 

 fluences of environment, such as food, mois- 

 ture, 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 chang- 

 ing conditions, and is thus an important means 

 of distinguishing species and varieties; not in- 

 frequently it 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, spread- 

 ing, 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 manage- 

 able in the vineyard. Productiveness, age of 

 bearing, and regularity of bearing are dis- 

 tinctive 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, the grape leaf-hopper, the flea- 

 beetle, berry-moth, root-worm, powdery-mil- 

 dew, downy-mildew, anthracnose, and other 

 insect and fungous troubles of this fruit. 



Minor structures of the plant. 



The structure of the bark is an important 

 distinguishing character for some species, but 

 is of little importance in identifying the va- 

 riety, 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 into 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, nodes 

 being more or less prominent, angular or flat- 

 tened, 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 ab- 

 sent, while in several other American species 

 it is very thin, and in still others quite thick. 

 The character of the diaphragm is best ob- 

 served in year-old canes. In studying the 



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