A STUDY OF GRAPE POLLEN AND WHAT THE 

 RESULTS INDICATE 



By N. O. Booth, State Experiment Station, Geneva, N. Y. 



The following investigations were carried on in the summer of 1902. 

 Their object was to determine, if possible, the reasons why certain varieties 

 of grapes are self-sterile. It was long supposed that self-fertility in a grape 

 merely meant that the pollen of that variety could not fertilize its own pistil 

 and the earlier students of the botany of the grape taught that such varieties 

 would be told by the recurved stamens which were always supposed to go 

 with self-sterility.^ Later investigations, which showed that certain of the 

 self-sterile varieties have long stamens." indicated that the recurving of the 

 stamens was not the cause nor even a character which always accompanied 

 self-sterility. Leaving out of consideration the recurving of the stamens as 

 a mechanical cause preventing pollen of a grape blossom from falling on its 

 own pistil and we have four other possible causes remaining: (1) What is 

 known to botanists as dichogamy or the pistil and pollen from the same 

 blossoms, and usually .same plant, maturing at different periods ; (2) lack 

 of affinity between pollen and pistil of the same plant; (3) the pollen on 

 the self-sterile sorts might be so scanty as to render fertilization improb- 

 able; (4) lack of viability in the pollen itself, making it impotent not only 

 on its own pistil, but also on all others. For reasons which will be discussed 

 in the latter part of this paper it was considered that the first and second 

 of these possible causes were not probable ones and our efforts were con- 

 fined wholly to investigating the third and fourth causes. This year observa- 

 tions were made on a great many different varieties as to the amount of 

 pollen present. All of these estimates were, of course, approximate, since 

 pollen is a material which it is impossible to measure exactly. These observa- 

 tions were made both with naked eye and simple lens. There were a great 

 many variations, but the variations did not appear to be particularly signifi- 

 cant. There were greater variations on different clusters of the same vine 

 than normally appeared on different vines of different varieties. The last 

 clusters of flowers to bloom, and sometimes the first, are usually not so well 

 supplied with pollen as those which appear at the height of the blossoming 

 season. Vines just coming into bearing and having only one or two clusters 

 on tihe vine were usually scantily supplied with pollen. With some of the 

 varieties even where there was no apparent cause in the condition of the 

 vine, the amount of pollen present was apparently insufficient to make pollina- 

 Ition at all certain. However, with most of the self-sterile varieties the 

 pollen was quite plentiful and apparently quite sufficient for pollinating pur- 



lEnglemann, Bushberg Catalogue, page 7, ed. IS'Jo. 

 =Beach. Bui. 157, N. Y. E. S. 



