Hybridization of Yitis Rotundifolia 
9 
layers of hard bast to appear in the bundle itself, either starting from 
one side or both sides and not reaching all the way across, or extending 
all the way across the bundle (Fig. 9). In only two instances did 
the bundle resemble that of Euvitis species, one of which is shown in 
Figuie 10. It is remarkable that the pattern of the phloem bundle as 
seen in cross section varies in the same stem to a very considerable 
extent, showing a lack of fixation of this character in a given stem 
(see Figs. 13-58). Some of the vines, however, are quite uniform in 
their pattern. Inasmuch as the cambium determines the formation of 
haid oi soft bast under unknown influences, m cases where the pattern 
in which these elements are laid down varies in the same stem, it would 
seem that the cambium of the stem must vary in its constitution. 
The size of the cells of the hard and soft bast is intermediate, as is 
the thickness of their walls, and their shape. The sclerencliyma bundle 
is more T . rotundifolia in character, though usually of larger size than 
this parent. 
Figures 11 to 38, inclusive, are camera lucida diagrams of the same 
magnification of T . vinifera, V. rotundifolia, and their hybrids. The 
hard bast of the phloem (also the bundle of sclerenchyma fibers) is 
shown stippled. Figures 13 to 38 show different degrees of inter¬ 
mediacy of character in the hybrids. Figures 13 and 15 show two 
adjacent bundles each with contrasting arrangements of the hard 
and soft bast. Such cases are quite common among the hybrids. 
Figures 14, 20, 25, and 33 show a progression in the range between 
the two types of arrangement. Only in Fgures 33 and 35 has the V. 
vinifera character approached dominance. Figure 34 shows the elements 
of the hard bast scattered indiscriminately through the soft bast. 
Rays. The character of the intervascular ray varies with the char¬ 
acter of the phloem. If the bundle is triangular as in V. rotundifolia, 
the ray immediately widens out by cell multiplication as in this parent 
(Fig. 7), but if the phloem bundle is broad and square the ray extends 
out without increasing in width as in V. vinifera (Fig. 10). In some 
cases the ray extends part of the depth of the bundle before widening 
out, showing most exactly the intermediate character (Figs. 8 and 9). 
Cortex. The cortex in the hybrids shows less fixation of a definite 
character than any other part of the stem, varying from a close 
resemblance to the staminate parent to a similarity to the pistillate 
parent. In most cases, the cortex is very much like that of the V. 
rotundifolia species. Only the two that have the Y. vinifera-like 
phloem have a cortex resembling that parent. In many of the vines 
there is a great variation in the same stem, one side being quite different 
from the other, or having patches of Y. vinifera-like cortex with large, 
loose, torn cells outside of a cortex otherwise resembling V. rotundifolia 
(Fig. 8 and 9). In the examples illustrated in Figures 7 and 8 the 
type of cortex shown is not typical for the entire section of the stem 
