Some Concepts in Mycology. William B. Brierley. 215 



The primary conception to which all these indications lead 

 is that of an organism as a physiological equilibration func- 

 tioning about a constant point, and of the environment as a 

 complex of forces with infinite capacity for adjustment. The 

 resultant of the interaction of the metabolic entity and the 

 environment is the growth form or "ecad." The constant or 

 speciiic function is the metabolic entity or physiological constitu- 

 tion and not the morphological individual which is merely the 

 visible expression of the reactions of the physiological constitu- 

 tion under particular conditions. 



It follows therefore that the mo/'/)Ao/o^/ca/ species concept — the 

 total of individuals possessing essentially similar morphological 

 fades — must be abrogated and in lieu thereof be substituted 

 the physiological species concept — the total of individuals 

 possessing essentially similar physiological constitutions. 



The morphological concept regards the species as an entity 

 in space: the physiological concept regards it as an entity in 

 space and in time. In other words the species is a dynamic 

 relation and not a static figure; it is an event and not a thing. 



Before concluding this brief consideration of the species 

 concept attention may be drawn to certain minor issues which 

 arise directly from it. Once having substituted the physio- 

 logical concept for the morphological one, and having accepted 

 the implications which such a viewpoint involves, it is recog- 

 nised that the systematic categorisation of fungi must coincide 

 with and take fully into account the known facts of their 

 behaviour. It is clear that many, perhaps most of the Linnean 

 species of fungi have no constant existence in fact; they are 

 merely aggregates of growth forms or "ecads." Many of them 

 are aggregates of elementary species, them.selves plastic; many 

 elementary species are aggregates of physiological or chemical 

 species, producing constant variationsunder recurrent conditions. 



The only exact method of species creation and specific 

 determination is by means of quantitative data derived from 

 cultural treatment under standardised physico-chemical condi- 

 tions, for this method alone reveals the physiological constitution 

 of the organism. To-day, merely to describe the essential 

 morphological characters of a particular growth form of a 

 fungus, and so create a new species — if that organism can he 

 groz&n in pure culture — exhibits not only a complete ignorance 

 of the philosophy of mycology, but a total inaptitude to appre- 

 ciate the developments of the subject and to apply to it the 

 elementary principles of scientific methodology. 



Certain fungi, however, cannot yet be grown in tubus, but 

 here surely the imperative need is not increase in the already 

 bewildering accumulation of binomial terms applicable largely 



