362 Report of tiii: lloKTicuLTLiasT of the 



izers for either partially self-sterile or completely self-sterile 

 varieties. From study of the effect of pollen from different vari- 

 eties upon the same self-sterile variety, it seems probable that 

 failure to set fruit may be due to several causes, such as dropping 

 off of blossom buds before they open or poor condition of the vine; 

 but the most common cause is imperfect pollinatitu due to im- 

 potent pollen. 



Lists are given of varieties, both strongly self-fertile and im- 

 perfectly self-fertile or self-sterile, which blossom very early, 

 medium early, in mid-season, medium late, late and very late. 



INTRODUCTION. 



In Bulletin 157 the writer presented a complete account, to 

 that date, of the investigations on the self-fertility of the grape 

 with which he had been engaged for several years.^ It was therein 

 shown that many of the cultivated varieties of American grapes 

 are either self-sterile or very imperfectly self -fertile. Such kinds, 

 when they are self -pollinated only, either bear no fruit or produce 

 more or less imperfectly filled clusters. In discussing the practi- 

 cal bearing of these discoveries upon the selection of varieties 

 and arranging them in vineyards so as to get the best results in 

 fruit production, attention was called to the fact that self-sterile 

 varieties may produce well filled clusters of fruit when the vines 

 are located near enough to other kinds to make cross-fertilization 

 possible. For this reason the general recommendation was made 

 that whenever the self-sterile or the imperfectly self-fertile kinds 

 are planted it would be well to put near them some other kind 

 which blooms at the same time. 



After Bulletin 157 was issued there came from several sources 

 requests for more definite information concerning the mingling of 

 varieties so as to provide for the proper fertilization of those kinds 

 which cannot produce well filled fruit clusters unless they are 



1 Beach, S. A. Self-fertility of the Grape. N. Y. Agr. Exp. Sta. Bui. 157. 

 Dec, 1898. 



