XI SEX 123 



of the double throwers, though both produced by the 

 same plant, differ in their relation to the factor (or factors) 

 for doubleness. Doubleness is apparently carried by all 

 the pollen grains of such plants, but only by some of the 

 ovules. Though the nature of doubleness in stocks is 



Fig. 27. 

 Single and double stocks raised from the same single parent. 



not yet clearly understood, the facts discovered by Miss 

 Saunders suggest strongly that the ovules and pollen 

 grains of the same plant may differ in their transmitting 

 properties, probably owing to some process of segregation 

 in the growing plant which leads to an imequal distri- 

 bution of some or other factors to the cells which give 

 rise to the ovules as compared with those from which 



