100 Sil Uli. 



The reappearance of the H(>egeri-t\\)e of capsule in onlj' 111 indi- 

 viduals out of a total of 2540 jjlants in the Fa of crosses between 

 B. Heegeri and an American liiotype of B. bursa-pasforis was at first 

 accepted as endence of a n()ii-;\rendelian behavior (Shüll 1907, 1909 b). 

 This ratio, 21-9 : 1. liid imt approximate so closely the ratio 15 : 1 as 

 to suggest clearly by itsolf the existence of two determiners for the 

 triangular cajisule, antl it was not until the ai)pearance of Nllsson- 



Fig. 3. Anatomical details of the capsule-wall of Bursa bursa-pastoris {A) and of 

 B. Heegeri (B). v lOO. Drawn liy J. JFariox Shui.l from microtome sections. 



Kliik's jiapers in wliicli duiilicate deteruiiners were demonstrated for 

 the presence of a ligula in Avena and for red pericarp-color in Triticuni 

 that a similar explanation was recognized as possibly available for the 

 unexpected ratio for cai)Sule-form in Bursa. 



The phenomena expected in the first four generations following any 

 cross in wbii-h ilu|iiii-ate deleiiiiiMeis are involved and in which dominance 

 is complete, may be eimsidered with advantage before proceeding to the 



