A .GEUDY OF GRAPE POLLEN? 

N. O. Bootu. 
SUMMARY. 
I. The self-sterility which is known to exist among many 
varieties of cultivated grapes is in many cases, if not all, due 
to a lack of potency in the pollen. 
It. This lack of potency is indicated in the pollen grains by 
a Shape which is quite different from that of potent pollen. 
III. It is also Shown in the arrangement of the pollen either 
dry or in liquid media. 
IV. Certain varieties of grapes bear pollen in which both the 
potent and impotent forms are mixed. Trial of this mixed 
pollen shows that the amount which germinates is approximately 
in proportion to the potent forms present. 
INTRODUCTION. . 
The following investigations were carried on in the summer of 
1902. They are a continuation of some work started by Pro- 
fessor S. A. Beach as far back as 1892, the general object of 
which was to determine what varieties of grapes are self-sterile 
and what other varieties are best to use as pollinizers for these 
self-sterile sorts.1 One of the first questions that comes up in 
such an investigation is, naturally: What causes self-sterility in 
the grape? There are several causes which might produce this 
condition: (1) What is known to botanists as dichogamy, or the 
pistils and stamens from the same blossom and usually from 
the same plant maturing at different periods; (2) lack of affinity 
between pollen and pistil from the same plant so that even 
*Reprint of Bulletin No. 224. 
1See Bulletins Nos. 157, 169 and 223 of this Station, 

