CHAPTEE XXIII 



MOULDS HYPHOMYCETES 



In their internal relations to each other, and their external 

 relations to the remaining orders, the Hyphomycetes are un- 

 doubtedly a well-defined and natural group. It may be, and 

 probably is, too rash an assumption to contend that all the 

 species are form-species, and only represent the conidial stage 

 of more perfect Fungi ; nevertheless a large nmnber of them 

 have been demonstrated to be merely transitionary, although 

 the precise mode of continuity has not been made clear. In 

 such a case the only reasonable course to adopt is to recog- 

 nise their morphological distinctions, and treat them, for all 

 purposes of classification, on the supposition that they may be 

 autonomous, and leave to the future, when their life-histories 

 are thoroughly known, to develop their true affinities and 

 relationships. The number of described species falls but little 

 short of 5000, and such a number is too large and important 

 to remain unrecognised, or without definite classification, within 

 the limits of present knowledge. Because many of the species 

 of Isaria have been ascertained to represent the conidia of 

 Cordyceps ; because certain of the subgenus Polyactis may be 

 the conidia of Sclerotinia; or even the entire genus Zygodesmium 

 may be so intimately related to resupinate Thelepliorae that 

 definite limit cannot be assigned between them, it would be 

 folly to expunge the whole upon suspicion, and thus increase 

 the difficulties in the way of the student in the pursuit of 

 knowledge along a path already sufficiently thorny and stony. 

 The general characteristics of the order are, tliat the spores, 

 or conidia, are naked or free, as they are in no other order, 

 except the Eymenomycetes and some of the Phijcomycdcs ; 



