40 DorsEy: VARIATION IN FLORAL STRUCTURES OF VITIS 
elongation of the shoot new tendrils become terminal, while the 
older tendrils and clusters assume a lateral position upon the 
stem, opposite and alternating with the leaves. Intermediate 
forms between tendrils and flower clusters are common. Durand 
(’o1) shows that in their origin and anatomical structure the grape 
tendrils and clusters are identical, and that they may change 
naturally one to the other. Tendrils frequently occur that bear 
a number of buds, the tendril retaining in such cases its irritability 
in the region of the buds and twining much in the same way as the 
normal tendril. 
The flower clusters vary considerably, both in size and in 
number éf clusters upon the cane, in the different varieties and 
species. Instances are common in the varieties of V. Labrusca 
in which five or more clusters are borne in succession on a single 
cane. This may be accounted for largely by the fact that in this 
species a tendril or cluster is usually borne opposite each leaf 
(“continuous tendrils’). In the other native species, which have 
no tendril or cluster for each third leaf (‘‘intermittent tendrils’’), 
the number of clusters per cane is reduced somewhat, the usual 
number being two or three. 
The staminate cluster usually bears more flowers, has greater 
fragrance, and blooms earlier in the open than the perfect form. 
The flowers on the main axis of the cluster open commonly from 
one to four days or more earlier than those on the “shoulder.”’ 
The blooming period of the different varieties and species varies 
much, and in the case of V. vulpina and V. bicolor the blooming 
periods rarely overlap, V. bicolor flowering last. 
THE FLOWER: The grape flower is hypogynous. The calyx 
is represented by a narrow rim at the base of the flower. The 
normal perfect form has five green petals with five stamens op- 
posite. Yellowish nectariferous glands occur between the stamens 
and are equal in number to them. There is a large sessile stigma. 
The carpels are from two to four in number, each usually with 
two ovules. The perfect form differs from the staminate merely 
in Possessing a fully developed and functional pistil, this usually 
being abortive to the extent that no stigma is developed in the 
staminate flower. 
Engelmann (’94) divides the pistil-bearing form into two types, 
