





1920] 



CHAMBERLAIN— BOTRYCHI I U 



397 



It would be interesting to compare the reduction divisions of 



the two species, but the problem of getting material of B. dis- 



sectum makes such a comparison difficult, if not impossible. Even 



with good preparations of critical stages, the interpretation might 



be uncertain, for, judging by a few figures in B. obliquum, the 2X 



number is w 7 ell over 100, and the 



chromosomes are tangled and hard 

 to count. 



Such evidence as we have would 

 indicate that B. dissectum is at least 

 partially, and probably entirely, 

 sterile. Unfortunately the natural 

 test which would prove or disprove 

 this theory — germinating the 

 spores— cannot be applied until 

 someone learns how to make these 

 baffling spores germinate. If the 

 spores of B. dissectum germinate, 

 we do not see why this species 

 should not occur in groups, like 



10 







it 



Figs. 10, 11. — Abortive spor- 



B. virginianum, B. obliquum, B. sim- 

 plex, and probably the other species. 

 In our opinion, the explanation 

 of the occurrence and behavior of . ang i um f b. dissectum, with many- 



B. dissectum is that the Species is layered wall and mass of mucilage 



a sterile mutant from B. obliquum. linin s <*vity from "*** s P°^ei)ous 



„,, .... . , . tissue has been resorbed ; X160: por- 



I he principal facts supporting this tion of sporangium of B . dissectum, 



theory are that B. dissectum, SO far showing spores of different sizes; 



as I have Observed in a five years' triangular spore doubtless abortive; 



stud}', never occurs except in asso- 

 ciation with B. obliquum, and that there is no evidence that it 



reproduces itself. 



It might be objected that mutants do not occur so frequently 



X350. 



must 



mi 



ratios. The total number of plants in the twenty- 

 four plots was 482 of B. obliquum and 19 of B. dissectum, a ratio 



wish in making 



