98 



Shull. 



the capsules, I assumed the existence of two independent factors, C and 

 7), the presence of either resulting in the development of the triangular 

 type of capsule characteristic of B. bursa-pastoris (SHULL 1911). Owing 

 to a rather large fluctuation in the ratios, the truth of my assumption 

 lacked adequate proof, and it remained at the close of the F 3 merely 

 an interpretation having 1 a certain degree of probability, like a number 

 of similar assumptions made by other investigators. Complete demon- 



Fig. 1. Capsules of fiursa bursa-pastoris (above) and of B. Heegeri. 



stration of the duplicate genes, C and D, has now been supplied by 

 the results of an ample F4, as will be seen in the tables given below 

 and in the graphic summary presented in Fig. 5. 



The superficial differences between the capsules of B. bursa-pastoris 

 and of B. Heegeri are now familiar to most students, but may be re- 

 called more easily by a reference to Fig. 1. The former have a strongly 

 flattened, triangular or obcordate form due to a spur-like inflation 



