POLLINATION AND STERILITY 301 



ability of the pollen or to defective pistils, as was demon- 

 strated by careful tests. ^ The three varieties notoriously 

 inter-sterile are Bing, Lambert, and Napoleon, and mixed 

 plantings of them will give little or no fruit unless they are 

 within the range of influence of some other variety that is 

 inter-fertilo with them. Of those studied, the Black Repub- 

 lican, Black Tartarian, and Waterhouse seemed to be the 

 most efficient pollinizers for this group. 



While not entirely germane to the sterility problem, it is 

 of interest to note that some members of the Duke group 

 of cherries and also some varieties of the sour cherries (P. 

 Cerasus) are capable of fertilizing some of the Bigarreaus. 

 The sour cherries are usually credited with being self-fertile 

 but there would seem to be many exceptions to this state- 

 ment. 



269. The almond. — Tufts ^ has shown that all the com- 

 mon varieties of almonds grown in California are self-sterile 

 to a large extent and certain of them are inter-sterile. The 

 honey bee is considered the best pollinating agent for the 

 almond. 



270. The grape. — The first important work in this 

 countrj^ on the sterility problem of the grape was that of 

 Beach, although Goff had previously shown that the variety 

 Concord would set fruit as well when the clusters were cov- 

 ered with a bag as when left open. Beach found that "Cul- 

 tivated American grapes show remarkable differences in 

 the degree of self-sterility of different varieties. Many of 

 them fruit perfectly of themselves. Others form no fruit 

 when cross-pollination with other varieties is prevented. 

 Most varieties are found between these two extremes, being 

 neither fully self-fertile nor completely self-sterile." After 



1 Gardner, V. R. Ore. Agr. Exp. Sta. Bull. 116. 191.3. 

 - Tufts, W. F. Almond pollination. Calif. Agr. Exp. Sta. Bull. 306. 

 1919. 



