STUDY OF GRAPE POLLEN. 249 



staminate and pistillate forms of to-day, since cross-fertilization would have 

 already been assured. 



The economic bearing of these results is quite apparent. In choosing 

 fertilizers for self-sterile grapes it will give us a means of selecting the best 

 varieties for this purpose without the long vinyard trials by sacking, etc., 

 which have heretofore been necessary. To the hybridist it may be of service 

 and it provides a means of determining the sexual status of varieties within 

 a 'single blossoming season. 



SUMMARY. 



I. — The self-sterility which is known to exist among many varieties of 

 cultivated grapes is frequently, if not always, due to a lack of potency in the 

 pollen. 



II. — 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. 



