124 MENDELISM CHAP, xn 



tion of characters which he had shown to exist in 

 peas and beans, and had probably looked forward 

 with some confidence to finding in Hieracium. More 

 than thirty years passed before the matter was 

 cleared up. To-day we know that the peculiar 

 behaviour of the hybrid Hieraciums is due to the 

 fact that they normally produce seed by a peculiar 

 process of parthenogenesis. It is possible to take 

 an unopened flower and to shear off with a razor all 

 the male organs together with the stigmata through 

 which the pollen reaches the ovules. The flower, 

 nevertheless, sets perfectly good seed. But the cells 

 from which the seeds develop are not of the same 

 nature as the normal ovules of a plant. They are 

 not gametes, but retain the double structure of the 

 maternal cells. They are rather to be regarded as 

 of the nature of buds which early become detached 

 from the parent stock to lead an independent exist- 

 ence, and, like buds, they reproduce exactly the 

 maternal characteristics. The discovery of the true 

 nature of this case was only rendered possible by 

 the development of the study of cytology, and it 

 was not given to Mendel to live long enough to learn 

 why his hybrid Hieraciums all bred true. 



