362 Report oF THE HorriIcuLTURIST 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 pollination 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 +457 was issued there came from several sources 
requests for more definite information congerning 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. Bul. 157. 
Dee., 1898. 
