61 VAN TIEGUEM AND LE MONNIER. 



the conjugating cells a series of repeatedly dichotomous 

 processes (figs. 11, 12, 13). These processes appear in the 

 first place upon one only of the arcuate cells, and in succes- 

 sive order. The first makes its appearance above upon the 

 convex side ; the succeeding ones to the right and left in 

 descending order: the last is in the concavity underneath 

 (figs. 7 and 8). It is only after the development of this that 

 the "first process makes its appearance above upon the other 

 cell (fig. 9), followed by the others in the same order. The 

 processes grow and dichotomise in the same order in which 

 they are developed. 



The first dichotomy always takes place in the plane, passing 

 through the point of dichotomy as well as the line join- 

 ing the centres of. the conjugated cells (figs. 9, 10) ; 

 the others follow in planes alternately at right angles 

 with one another. The two branches of the first dicho- 

 tomy are slightly unequal; that which is situated next the 

 zygospore is the most developed, and lying upon it dicho- 

 tomises again repeatedly, interlacing its branches so as 

 to envelope and protect the zygospore. These dichotomous pro- 

 cesses are nothing more than branches of the arcuate cells ; 

 in fact, when the " vice " is arrested in its development, it is 

 not unusual to see one or more of the processes already formed 

 develope into ordinary mycelial hyphse (fig. 14). During 

 all these changes, while the zygospore enlarges, the wall of 

 the arcuate cells becomes coloured brown. This coloration 

 is more marked on the convex side, and it shows itself first 

 in the cell on which are produced the first dichotomous 

 branches and which long retains a darker tint than the other. 

 The zone of origin of the processes and the processes them- 

 selves have their wall of a deep black, while the walls of 

 the conjugated cells which continue to clothe the zygospore 

 during the whole period of its development is itself a bluish- 

 black (figs. 11, 13). When its development is complete the 

 zygospore may attain ^ mm., but many occur which are much 

 smaller. It is more developed on its external than upon its 

 internal side, and its lateral faces by which it is attached to 

 the teeth of the vice are slightly inclined one to the other, 

 which is the result of the curvature of the primary cells. By 

 pressure the black, thin, and brittle coat which envelopes the 

 zygospore is ruptured, and the coat of the zygospore itself is 

 exposed as a thick, cartilaginous membrane studded by large 

 irregular protuberances. The contained protoplasm, like that 

 of all zygospores, is very rich in fatty matters. The dichotomous 

 processes which interlace their branches round the zygospore 

 as if to protect it distinguish the reproductive apparatus of 



