138 BOTANICAL GAZETTE [august 



chambers kept at this temperature than under ordinary labora- 

 tory conditions. The tubes containing the pure cultures were 

 treated in the same manner, but no zygospores appeared, showing 

 that the cultures were pure and not a mixture of strains. 



Cunninghamella has been regarded by Blakeslee as dioecious, 

 and therefore no zygospores should appear unless both sexual 

 strains are present. As both strains of C. hertholletiae had not 

 yet been found, I contrasted all my cultures of this species with 

 Blakeslee's plus and minus strains of C. echinulata, hoping to 

 secure imperfect hybridization, and thus, if possible, to determine 

 the plu^ or minus nature of my strains. Many series of plates 

 were made in which the cultures were contrasted with both strains 

 of C. echinulata, but, although different media were used and the 

 plates were subjected to different temperatures, I was unable to 

 obtain imperfect hybridization in a single instance. 



Both strains of Blakeslee's Mucor V. were also used with a 

 similar result. When C. echinnlata plus and minus, as separated 

 by Blakeslee, were contrasted with his Mucor V. plus and minus, 

 imperfect hybridization took place. Moreover, when both the 

 sexual strains of either of them, Mucor V. or C. echinulata, were 

 themselves contrasted, the production of zygospores showed that 

 the strains of these 2 test species had not lost their sexual 

 vitality. 



Experimental work 



I have 34 different cultures of the Mucorineae which were 

 contrasted with each other as indicated in table I. Cultures 1-26 

 inclusive are strains of C. hertholletiae, no. 21 being an authentic 

 culture which was obtained from Holland. Cultures 27-31 are 

 strains of C. echinulata, and of these 27 and 28 are C. echinulata, 

 plus and minus as separated by Blakeslee. Cultures 32 and 33 

 are Mucor V. minus and plus as separated by Blakeslee, and 

 34 is an authentic culture of C. elegans which was also obtained 

 from Blakeslee. 



contrast series a 



Having been unable to get any sexual reaction by contrasting 

 the different strains of C. hertholletiae with C. echinulata plus and 

 minus, I contrasted C. elegans no. 34 with all my other cultures. 



