3i8 Journal of Agricultural Research voi. iv, no. 4 



made. These seedlings have thrown much light upon the inheritance of 

 various factors, but they have been so uniformly lacking in vigor as to lead 

 to the belief that only through crossbreeding can we hope to produce 

 improved varieties. 



INHERITANCE OF CHARACTERS 



The grape characters discussed in the following pages are those for 

 which sufficient data are available to make such a discussion of value. 



SELF- STERILITY 



On the basis of flower type, grapes may be divided into three classes: 

 (i) True hermaphrodites; (2) hermaphrodites functioning as females, 

 owing to completely or partially abortive pollen; and (3) pure males with 

 the pistil absent or rudimentary. Among these classes there are two 

 types of stamens: Those with upright filaments and those in which the 

 filaments bend backward and downward soon after the calyx cap falls off. 

 According to Dorsey (5), this is due to the cells of the outer surface of the 

 reflexed stamens being smaller and having thinner walls. 



So far as observed at the New York Station, all pure males have upright 

 stamens. Among the two classes of females Beach (i) found that only 

 those varieties with upright stamens were capable of producing market- 

 able clusters of fruit when self-fertilized. At the same time he reported 

 nine varieties with upright stamens to be self-sterile. Since Beach pub- 

 lished his report further work at this Station with three of these nine 

 varieties has proved them self-fertile, and it is probably safe to say that 

 all varieties with upright stamens are self-fertile, though in varying 

 degrees. Rfeflexed stamens are always correlated with complete or nearly 

 complete self -sterility. Reimer and Detjen (6) found this last conclusion 

 to hold also with Vitis rotundifolia, a species not studied at this Station. 



The cause of self -sterility in varieties with reflexed stamens seems to be 

 a lack of viability in all or a large part of the pollen of such varieties. 

 Booth (2) found that such pollen was quite irregular in form and would 

 not germinate in sugar solutions. Reimer and Detjen (6) state "the 

 pollen of all the present cultivated [female] varieties [of V. rotundifolia] 

 is worthless." Recently Dorsey (4) has ascribed the cause of this self- 

 sterility to a degeneration in the generative nucleus. While this im- 

 potency may be absolute in many of the varieties, in some at least it is 

 only relative. Frequently viable pollen will be found mixed with the 

 usual misshapen, abortive pollen of the self -sterile varieties, and nearly 

 a hundred pure seedlings of the varieties which Beach (i) reported as 

 totally self-sterile have been grown in the Geneva Station vineyard. The 

 degree of sterility seems to depend to some extent upon the condition of 

 the vine due to environmental factors. 



