I40 BOTANICAL GAZETTE [august 



As a result, imperfect hybridization took place between it and nos. 

 3, 8, 12, 13, 21, 24-26, and 32. Culture 25 is Blakeslee's Mucor 

 V. minus, therefore the culture of C elegans with which it reacted 

 would be plus. It also reacted with culture 21, which is the 

 authentic culture of C. bertholletiae. Since I was unable to get a 

 sexual reaction with the different strains of C. bertholletiae when 

 contrasted directly with Mucor V. plus and minus, I had to deter- 

 mine their sexual character by this indirect method. Since, there- 

 fore, C. elegans no. 34, because of its reaction with Mucor V. 

 minus, would necessarily be plus, according to Blakeslee, C. 

 bertholletiae no. 21 would be minus since it reacted with C. elegans 

 no. 34. On the other hand, the cultures which did not react with 

 no. 34 would be regarded as either plus or neutral. 



CONTRAST SERIES B 



Since I had thus determined that the sex of no. 21, the 

 authentic culture of C. bertholletiae, was minus, I then contrasted 

 it with all my cultures of this species, and normal zygospores 

 were formed with nos. i, 2, 3, 7, 9, 10, 13, 14, 16, 17, and 20, while 

 imperfect hybridization took place again with no. 34, the authentic 

 culture of C. elegans. All of these, therefore, on a basis of Blakes- 

 lee's theory, should be regarded as certainly plus. In contrast 

 series A, however, it was proved that cultures 3 and 13, like no. 21, 

 were minus, but in the present series B they both formed normal 

 zygospores when contrasted with no. 21. If we assume, therefore, 

 that the species is dioecious, it is impossible on the theory of 

 heterothallism to account for the production of normal zygospores 

 in series B as a result of the interaction on no. 21 with mycelia 

 which had been demonstrated to belong to the same sex. 



CONTRAST series C 



As we have seen, cultures of C. bertholletiae no. 9 formed zygo- 

 spores in series B with no. 21, which in series A was shown to be 

 minus. C. bertholletiae no. 9, therefore, according to the theory 

 of Blakeslee, should be regarded as plus. This plus strain no. 9 

 was then contrasted with all the other cultures of C. bertholletiae, 

 and as a result formed zygospores with nos. 3-8, 12, 13, 15, 20, 

 and 21. This presumably plus strain, therefore, formed zygo- 



