Dodge : Life History of Ascobolus magnificus 127 



Compare Neger's figures of Melanospora marchica, Papulo- 

 spora stage (15) with my figures, PI. 8, also compare the "groups 

 of ehlamydospore-like structures" of M. papillata (Hotson, PI. 

 2, fig. 7) with my text figures 22 and 23 ; and further, the fC Acfe* 

 moniella type" of spore of M. cervicula (Hotson, PI. 3, fig. 17) 

 with those shown in text figs. 27, 28, and one is struck with the 

 close parallelism between the asexual reproductive bodies of 

 Melanospora and those of Ascobolus magnificus and the spore 

 balls of Urocystis type. As noted we have been unable to obtain 

 ascocarps from one-spore cultures of P. magnifica. Further- 

 more, I have no record of obtaining ascocarps from a one-asco- 

 spore culture of A. magnificus. 



Two Strains Necessary for Sexual Reproduction 



I have stated in connection with the description of the pri- 

 mordia that the ascogonia and antheridia ordinarily (or perhaps 

 always) arise from different hyphae. This fact early suggested 

 the reason for the sterility of one-spore cultures. If one sows 

 ascospores in a dung culture he may obtain ascocarps. If they 

 are sowed in an agar medium under proper conditions germina- 

 tion may take place rarely, and I have frequently obtained asco- 

 carps from such cultures, but I have noticed that when one or 

 two transfers of mycelium are made from these fertile cultures 

 the subcultures are apt to be sterile. Thi9 is especially true 

 where the ends of the hyphae are cut off and transferred from 

 young cultures. I have planted a single spore on agar in petri 

 dishes and on sterile dung in jelly glasses in several hundred 

 cases without obtaining a single germination, so rarely do the 

 ascospores germinate. On August 16, 1919, I planted ascospores 

 on agar in each of ten petri dishes, heating the cultures at 6o° C. 

 for twenty minutes. After twenty-four hours no germination 

 had taken place. On September 2, mycelium was found in seven 

 of the dishes and papulospores were present in each case, but 

 there were no primordia or ascocarps. Transfers of mycelium 

 were made to tube and plate cultures and on September 4 steril- 

 ized horse manure in jelly glasses was inoculated with the strains 

 numbered 1, 2, 3, 4 and 5. Strain 6 was lost and strain 7 was 



