Ill] PLECTASCALES 57 



possible to regard this fusion as representing the non-sexual fusion in the ascus 

 which characterizes the members of other groups of Ascomycetes, and to 

 look upon the gametophyte and sexual organs as having wholly disappeared. 



On the other hand, the fact that fusion is between separate cells, and 

 not between nuclei located in the same cell, and the further fact that the 

 fusing cells sometimes differ in size and behaviour (and not infrequently 

 fail to fuse) recall characteristics of the sexual process in other fungi, and 

 indicate that we are dealing here with forms in which the vegetative hyphae 

 are gametophytic, the uniting cells are gametangia, the diplophase is repre- 

 sented only by the fusion nucleus, the ascospores are formed directly in the 

 oogonium, and the anomalous second fusion does not occur. In Guillier- 

 mondia, where the fusion cell buds out a daughter cell in which the asco- 

 spore is produced, we may conceivably have the rudiment — or the vestige — ■ 

 of an ascogenous hypha, and inDipodascus the outgrowth of the gametangium 

 after fertilization may have a similar significance. Should the Endomyce- 

 taceae prove to be primitive, the history of the higher Ascomycetes becomes 

 that of the interpolation of a vegetative sporophyte between fertilization 

 and meiosis. 



The Flectascales, as defined above, include the following families : 



Asci naked. 



Vegetative cells forming a mycelium ; asci distinct 



from vegetative cells Endomycetaceae. 



Vegetative cells single or loosely attached ; asci not 



differentiated from vegetative cells Saccharomycetaceae. 



Asci surrounded by loosely interwoven hyphae Gymnoascaceae. 



Asci surrounded by a definite peridium. 

 Ascocarp subaerial 



Sessile Aspergillaceae. 



Stalked Onygenaceae. 



Ascocarp subterranean 



Peridium distinct from walls of ascocarp ; 



spore mass powdery at maturity EL.A.PHOMYCETACEAE. 



Peridium continuous with walls of asco- 

 carp ; spore mass never powdery Terfeziaceae. 



Endomycetaceae 



In the Endomycetaceae the mycelium is usually well developed and 

 bears numerous asci each of which is either the product of a separate and 

 presumably sexual fusion, or parthenogenetically produced. Oidia, chlamy- 

 dospores and yeast-like conidia may be formed. The majority of the 

 Endomycetaceae are saprophytic on sugary substances or on exudations 

 from plants. Endomyces Mali is described as an active parasite on apples 

 and various species are parasitic on other fungi. The principal genera are 

 Eremascus and Endomyces. 



