2o8 Transactions British Mycological Society. 



investigations dealing with variations in the size, shape and 

 colouring matter of the spore. 



That the essential morphological characters of fungal spores 

 are not necessarily constant under different conditions has been 

 shewn by Stevens and Hall (44) for species of the genera Septoria, 

 Ascochyta, Volutella, Spermoedia, Coniothyrium, Epicoccus, 

 Colletotrichum, Phyllosticta, Alternaria, Sclerotinia and Dip- 

 lodia; by Mutto and Pollacci(29) for species of Coniothyrium 

 and Phyllosticta; by Stakman(4i, i) for Puccinia graminis; 

 by Long (22 a) for Puccinia ellisiana and Puccinia Andropogonis; 

 by Moreau(28) for Spowdinia grandis; by Elliott(ii) for Macro- 

 sporium and Alternaria; by Gaiimann(i4) for Peronospora; 

 by Beach (3) for Septoria and by numerous investigators for 

 species of many other genera of fungi. 



There is thus a considerable body of evidence to shew that 

 the essential descriptive characters of fungal spores may largely 

 be determined by the conditions under which the fungus 

 develops, and that environmental changes may result in 

 modification of spore characters. Nor is it only the morpho- 

 logical features of the spores which are altered: the whole 

 structure and facies of the organism may undergo transforma- 

 tion. 



In bacterial studies such artificially induced modifications of 

 the organism constitute a major part of the common laboratory 

 technique, and are utilised extensively and often exclusively in 

 specific determinations. 



In mycological studies, however, although cultural modi- 

 fications are the daily experience of laboratory workers, they 

 are still practically unrecognised by the systematist, and when 

 recognised either neglected or regarded as abnormal or bizarre 

 phenomena "idle to speculate upon." Innumerable instances 

 of such morphological transformations are scattered through 

 the literature of three decades, or could be given out of one's 

 own experience. 



Thus after a very thorough and intensive cultural study of 

 certain species of the genus Penicillium, Thom(45) remarks 

 "In experimental cultures changes in the chemical nature of 

 the medium or in the conditions, or both, have been found to 

 produce great changes in the morphology of the fungi studied. 

 With the exception of a few fundamental group or generic 

 characters nearly every attribute used in specific description 

 has been shewn to be a reaction to environment, hence change- 

 able with such environment (for some species at least)." And 

 again, "Many species differ so materially in gross characters 

 when grown upon these different media that successive cultures, 

 if not known to be pure transfers, might be supposed to be 



