560 Report of the Horticulturist oe the 



Why do not the self-sterile varieties become fertilized after be- 

 ing self-pollinated? Three explanations suggest themselves: 

 First, the stigma may not be receptive when the pollen is dis- 

 charged and the pollen may perish before the tubes enter the 

 stigma; or, second, either the pollen or the pistils may be imper- 

 fectly developed; or, third, the pollen may be incapable of fer- 

 tilizing a pistil of its own variety, because of a lack of affinity be- 

 tween the two. 



While assisting the writer in crossing grapes in 1898 Close 

 found that while castrating a cluster of Mills some anthers burst 

 and allowed the pollen to escape, although the blossoms had not 

 yet opened. After castrating several blossoms in the cluster he 

 removed the rest and covered the cluster with a paper bag to ex- 

 clude pollen from other flowers. The bag was not opened till 

 the fruit on the vine was well developed. It was then found that 

 fourteen fruits had developed. These ripened perfectly although 

 eight of them were seedless. Fig. 10 is reproduced from a photo- 

 graph of these fruits. Here is an instance in which self-pollina- 

 tion was effected by hand, before the natural blossoming period 

 arrived, with the result that the pollen retained its vitality till the 

 pistils became receptive and then performed its function success- 

 fully. 1 Millardet has found that stigmas of blossoms castrated just 

 before blooming may retain their vitality without pollination for 

 eight or nine days and that grape pollen may retain its vitality for 

 two weeks, at least. 



The evidence which has thus far been obtained does not support 

 the idea that the failure of self-pollinated blossoms to set fruits can 

 be attributed to the discharge of the pollen before the stigma be- 

 comes receptive. 



In several instances pollen of self -sterile grapes has been applied 

 to other varieties by hand and as a result perfect fruit has deveb 



l Millardet, A. L'Hybridation de la Vigne. Paris: 27, 31. 1S91. Millardet 

 quotes Castel as affirming that he had repeatedly caused the hybridization of 

 the grape by dusting the stigmas with pollen of the preceding year. In view 

 of the results of the test by Close, Castel's experiments should be repeated 

 with precaution to prevent self-pollination when the blossoms are being cas- 

 trated. 



