SEXUALITY IN CUNNINGIL\MELLA^ 



Owen F. Burger 



The factors governing sexual reproduction in the Mucorineae 

 have been regarded by various writers as due to the nutritive 

 characters of the medium, the humidity of the surrounding atmos- 

 phere, the oxygen supply, and, lastly, the presence of conjugating 

 male and female strains. So conflicting have been the theories 

 that it is evident that the conditions controlling the production of 

 zygospores are not so simple as many persons have supposed. 



When Ehrenberg first discovered the zygospores of Sporo- 

 dinia grandis, he regarded their formation as a process comparable 

 to conjugation in Spirogyra. Since it was noticed that among the 

 Mucorales zygosporic formation did not always occur, different 

 workers gave their attention to the factors controlling their pro- 

 duction. DeBary, after working with Rhizopus, came to the 

 conclusion that the lack of oxygen was the controlling factor. 

 He found that the zygospores were produced in a closed tube 

 more abundantly than in a tube opened to the air. Van Tieghem 

 repeated the work of DeBary, and confirmed his views that desic- 

 cation could account for zygosporic formation in Absidia septata. 

 On the other hand, he believed the zygospores described by 

 Brefeld, in Piptocephalis and Sporodinia, were brought about by 

 unfavorable food supply. Bainier also thought that the environ- 

 ment influenced sexual reproduction, but he maintained that the 

 formation of sexual organs was dependent on a nutritious rather 

 than a poor substratum. Zopf found Piloholus producing zygo- 

 spores, but ascribed their production to the fact that it was 

 attacked by the parasites Pleotrachelus fulgens and Syncephalis sp. 

 Klebs maintained that their formation is induced by increased 

 humidit}', which hinders transpiration. Falck, on the other 

 hand, found that humidity and transpiration within normal limits 

 have no effect on the production of zygospores. Brefeld main- 

 tained an agnostic attitude, and in a series of papers denied that 



' Contribution from the Cryptogamic Laboratories of Harvard University, no. 84. 

 Botanical Gazette, vol. 68] [134 



