Self Sterility and Cross Sterility in the Apple. 63 



was recorded in connection with the data on transplantation. 

 These data all bear on the problem of self sterility and cross 

 sterility in the apple and will be used in connection with this 

 study. The publication of the results obtained from the 

 crosses, the bearing ability of the seedling trees, and the quality 

 of the resulting apples will form the basis of other reports on 

 the orchard work of the Biological Laboratory. 



The sterility tests are made in four ways. To test for self 

 sterility the unopen buds are inclosed in a ten pound paper bag. 

 These bagged flowers are treated in two ways; (a) the bags 

 are left undisturbed until the fruit is set; (b) the bags are 

 opened at the height of the bloom and the pollen from the an- 

 thers brushed over onto the stigmas, the bags replaced and left 

 until the fruit is set. 



The tests for cross sterility are likewise made in two ways; 

 sterility between members of the same variety and sterility be- 

 tween different varieties. All of this was done with emascu- 

 lated flowers, the pollen transfers being made with camel's hair 

 brushes. In each case the flowers, both emasculated and pol- 

 linated were covered with paper bags, care being used in the 

 removal for pollination and subsequent replacing of the paper 

 bag to prevent accidental pollination. 



When the fruit is set the paper bags used in the pollination 

 work are replaced with cheese cloth bags. All the crosses made 

 are tagged with a distinctive number to prevent any pedigree 

 errors. 



Self Sterility and Self Fertility. 



In table I are shown the result of the crosses involving the 

 pollen from a flower cluster being placed on the pistils of that 

 same flower cluster or a different flower cluster of the same 

 trees or different trees. The flower clusters which are only 

 bagged depend, of course, on chance agencies to transport the 

 pollen from the anthers to the stigmas. Those flowers which 

 have the pollen transferred from the anthers of the flower clus- 

 ter to the stigmas of the same flower cluster by means of the 

 camel's hair brush brushing the pollen across from the one to 

 the other eliminate this chance element. The average number 

 of flowers worked to each flower- cluster was six.. The results 



