﻿338 BOTANICAL GAZETTE [may 



histories throughout the group. Nevertheless, the various types 

 of sexual reproduction seem very diverse when compared with 

 one another and with conditions in the algae and other fungi. 



However, should the coenogamete be established as a primi- 

 tive type of sexual organ here as in the Phycomycetes, certain 

 difficulties will be removed. The oogonium (archicarp) would 

 be considered a development from the coenogamete along a well- 

 established evolutionary line, that of numerical nuclear reduction. 

 The evolutionary trend of the coenogamete would then be toward 

 the uninucleate oogonium (Sphaerotheca) following the tendency 

 of sexual evolution so well recognized in the algae. The groups 

 of the Discomycetes and Pyrenomycetes would then readily 

 arrange themselves according to the structure of the ascocarp 

 and general vegetative complexity. 



There would be left the lichens and Laboulbeniaceae, whose 

 trichogynes at least suggest the Rhodophyceae, while in the 

 latter group there are certain histological resemblances to this 

 same group of algae. Granting these possible affinities, it is 

 nevertheless very difficult to conceive the multicellular trichogyne 

 as derived from the simple structure of the red algae. It must 

 also be borne in mind that the structure of the ascocarp, 

 especially among the lichens, gives no suggestion of a cystocarp, 

 but, on the contrary, presents a structure identical with the 

 fructification of other Ascomycetes. Were it possible for the 

 coenogamete to develop a multicellular trichogyne (there is a 

 multinucleate one in Pyronema) then evolutionary lines might 

 be established that would lead very naturally into the lichens 

 and Laboulbeniaceae. Such trichogynes would be another form 

 of expression of this remarkable structure, the coenogamete, 

 which is able to utilize superfluous protoplasm in such a variety 

 of ways. 



In this connection it is interesting to sum up the various ways 

 in which the superfluous protoplasm of a coenogamete may assert 

 itself. It may form a periplasm of importance in developing the 

 spore wall (Peronosporales). It may form a surrounding tissue 

 from such periplasm (Araiospora). It may develop a conjugat- 

 ing tube (Pyronema). And finally we suggest the possibility of 



