﻿336 BOTANICAL GAZETTE [may 



might be satisfied by the fusion of the gametangia (coenogametes ) 

 in pairs whereby the gamete nuclei would be able to unite two by 

 two in a common protophismic medium. This process would 

 take the place of the conjugation of motile gametes in water, and 

 apparently satisfy all the hereditary demands as far as nuclei are 

 concerned. The structure resulting from the fusion of these 

 simplest coenogametes would be very similar to the zygospore 

 of the molds. 



Although there are no coenogametes among the algae, the 

 sexual processes in the Conjugales have some features worth 

 noting in this connection. In the desmids the gametes slip 

 from the parent cells and fuse as naked masses of protoplasm. 

 But in the filamentous Zygnemaceae and Mesocarpaceae the 

 energids (gametes) remain In the respective parent cells which 

 push out conjugating processes. The conjugating processes are 

 surrounded by a cell wall so they are in every respect similar to the 

 conjugating tube of Pyronema or the receptive papilla of the Per- 

 onosporales, excepting that they emanate from a uninucleate cell 

 instead of a'coenocyte. It is important to note that the conjuga- 

 tion processes in the Phycomycetes and Ascomycetes have their 

 analogies in the algae, for it might be suggested that the develop- 

 ment of such a structure by a coenogamete would be difficult. 

 On the contrary, it seems the natural expression of any cell with 

 chemotactic tendencies, whether uninucleate or multinucleate, to 

 fuse with its neighbors. It is very probable that the develop- 

 ment of such a conjugating tube in a coenogamete would be at 

 the point where formerly the naked motile gametes were dis- 

 charged, for that place is evidently the seat of important cyto- 

 plasmic activities. 



To sum up our conception of the Phycomycetes, we must 

 regard them as a group of several independent phyla. The 

 Chytridiales in morphology and life-history are the lowest and 

 resemble the algae at the level of the Protococcales. Mono- 

 blepharis, and probably several other isolated genera, seem most 

 closely related to heterogamous algae. The Entomophthorales 

 are too highly specialized to be easily derived directly from 

 algal ancestry and need not be considered in this paper. There 



