g, 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 disting