294 INTRODUCTION TO THE STUDY OF FUNGI 



colouring matters, such species being distinguished as chromo- 

 genous ; in the exciting of various fermentations, and hence 

 called zymogenous ; and in the decomposition of the humours 

 of animal and human bodies, whereby diseases arise, and these 

 are pathogenous species. Some authors prefer to group them 

 as pathogenous, zymogenous, and saprogenous. 



The classification of this order must still be regarded as 

 imperfect and transitionary, and will be the subject of much 

 change in proportion to the development of knowledge which 

 experience will afford. There are some. who are prepared to 

 accept all the morphologically or physiologically distinct forms 

 as different species, and with them the number of genera and 

 species would be large. There are others who hold that most 

 of the Schizomycetes pass through a series of adaptive forms, 

 influenced by surrounding circumstances, and modified by 

 external conditions, so that at one time it may have the form 

 of a Bacillus or of a Bacterium, of a Micrococcus or a Spiro- 

 chaete. In this latter case the number of genera and species 

 would be reduced to their lowest expression. Perhaps, in the 

 present state of knowledge, the wisest course is to accept the 

 various forms as they appear to be, on the presumption that 

 they are autonomous, and leave condensation and reduction to 

 the gradual operations of the future, and the verification of 

 facts or assumptions, in the light of experience. The arrange- 

 ment adopted by Saccardo recognises three primary groups, or 

 families. The Trichogenae, with three evolutionary states — the 

 filament, the rod, and the coccus — of which the filament is the 

 primary condition, vaginate or evaginate, fixed at the base or 

 radiating from a central point, rarely entirely free ; rods and 

 cocci included in the filaments. The second family, Baculogenae, 

 also with three evolutionary states — rods, filaments, and cocci. 

 In this group the rod is the primary state, the filament 

 secondary, never vaginate, or fixed, or radiating, formed by the 

 indefinite prolongation of a single rod or the union of many. 

 The third family, Coccogenae ; there is but one state, that of 

 the coccus. Beyond this it would not be profitable to follow 

 the subdivisions. 



No one can doubt for a moment that the pathogenous 

 species are of immense importance as objects of study and 



