94 ALBERT FRANCIS BLAKESLEE. 



larger size but also by the curved outgrowths that arise from its 

 suspensor. It will be observed further from these figures that 

 the female gamete is formed from a rather stout branch which 

 appears to have been attracted by Mucor V. ( ) and drawn 

 away from the delicate termination of the main axis with which 

 it would normally have conjugated (cf. Fig. 8). In order to 

 obtain such reactions as shown in Figs. 20-24, some care had 

 to be exercised in regard to the condition of the culture. If the 

 nutrient is too favorable for growth the filaments will choke 

 the channels and cannot be followed. If the nutrient is de- 

 ficient, conjugations will not occur. The depth and width of 

 the channels and the time at which they are cut must be care- 

 fully regulated or no reactions can be observed. They have 

 been obtained and studied in a sufficient number of cases, how- 

 ever, to leave no doubt as to their occurrence. Mucor V. is 

 the only form whose ( ) race was found to give a sexual reaction 

 with A. spinosa. 



The sexual reaction of A. spinosa w T ith the ( + ) race of Mucor 

 V. is entirely different from what has just been described. At 

 the line of contact between the two mycelia, the filaments are 

 much branched and imperfect hybridizations are abundant. 

 Figs. 1 8 and 19 show simplifications of this condition from living 

 material. Fig. 17 shows gametes cut off from A. spinosa, 

 while Figs. 14-16 show such gametes transformed into dark 

 thick- walled azygospores. Fig. 15, which shows the progamete 

 of Mucor V. ( + ) rounded off and in bare contact with the 

 azygospore of A. spinosa, is a typical condition. 



The (+) race of Absidia car idea (A ( + ), Figs. 8-10) shows 

 a less active sexual reaction with A. spinosa but similar to that 

 shown by Mucor V. ( + ), and the same is true of A. cylindrospora 

 and Mucor N. The ( + ) strains of all four dioecious species 

 mentioned are capable of stimulating the production of small 

 male gametes from filaments of A. spinosa and their transfor- 

 mance into dark thick-walled azygospores. Unfortunately 

 it has not yet been possible to bring these azygospores to ger- 

 mination. It would be interesting to discover if their germina- 

 tions would give rise to unisexual male mycelia. 



Judging from the reactions just described between Absidia 



