10 
Hybridization of Vitis Rotundifolia 
but only for a small number of bundles, more striking because of their 
irregular occurrence. 
The indeterminate location of the phellogen seems to be the cause of 
this variation. It appears in the photomicrographs as a whitish layer 
due to the stain washing out of the suberized tissues. Its position 
varies not only in different vines but usually in the same vine (Fig. 7). 
In some cases, it is just under the epidermis as in V. rotundifolia. In 
other cases, it is inside of the sclerenchyma bundle as in the other 
parent (Fig. 10). Quite often there is an isolated layer of suberized 
tissue surrounding only one bundle of sclerenchyma fibers (Fig. 29). 
Frequently all three of these positions for the phellogen are found in 
the same stem, and in some instances at the same point in the stem. 
Usually the cortex inside the cork cambium resembles the 1 . rotundi- 
folia parent, and that outside the V. vinifera parent (Fig. 9). Lenticels 
were present only where the phellogen is immediately under the 
epidermis. This scattered distribution of the cork cambium is respon¬ 
sible for the exfoliation of the bark in small flakes. 
In Figures 11 to 38 the phellogen is shown in solid black. Figures 
11 and 12 represent the parents, and Figures 13 to 38 the hybrids, 
which show all degrees of the cork cambium character expressed in 
the parents. Bundles diagrammed are more or less typical for the 
particular stem, but do not by any means represent the condition of 
each bundle of the stem. In Figure 13, for example, the phellogen 
occurred outside of only a few bundles at this particular location 
which is used to illustrate the arrangement of hard and soft bast in 
the phloem. Such cases as shown in Figures 19, 24, 37, and similar 
ones, usually occurred only in small patches of the circumference of 
the transverse section. In Figure 31 isolated suberized cells are 
scattered through the cortex. 
VITIS BOURQUINIANA, Variety Herbemont 
The stem of V. bourquiniana so closely resembles that of V. vinifera 
that a detailed description of it is unnecessary in this place. If any 
difference exists in the characters in question it is perhaps that the 
cells have thinner walls (Fig. 45). 
V. BOURQUINIANA X V. ROTUNDIFOLIA HYBRIDS 
It was possible to examine only four of the hybrids of this cross. 
The expression of the intermediate character is similar to that in the 
V. vinifera hybrids. There is, however, no example of the phloem 
bundle resembling that of the Euvitis parent and the resemblance was 
predominantly toward the other parent. In view of the small number 
of vines studied, this was hardly significant. 
Diagrams of these hybrids are shown in Figures 39 to 44, inclusive, 
Figures 39 and 40 being from one vine, and Figures 43 and 44 from 
