Some Concepts in Mycology. William B. Brierley. 209 



different species; but when returned to the original media and 

 conditions these forms have immediately produced the charac- 

 ters and reactions first found, with a large degree of uniformity." 



Fifteen years ago Smith and Swingle(4o) wrote of their 

 Fusarium oxysporitm, "...This fungus shewed a number of 

 very striking variations. For this reason it is impossible to 

 give a general description that will hold universally." After 

 quoting descriptions of eleven old species of Fusarium from 

 potatoes, the authors conclude as follows: "Judged by the 

 above descriptions, we have had a half dozen or more species 

 of Fusarium in our culture tubes, some of them 'new species,' 

 and yet all were the product of a single spore. This does not 

 mean that there have been in our cultures any very wonderful 

 transmutations of one thing into another, but only that organ- 

 isms respond to their environment, and that 'species descrip- 

 tions ' of the kind cited have not taken this fact into considera- 

 tion, and consequently are worthless for scientific purposes. 

 This is not a new idea, but it is a fact to which the attention of 

 systematic mycologists might be directed profitably at frequent 

 intervals." 



A few years later Stevens and Hall (44) drew attention to 

 this same fact and wrote " If a fungus can be easily changed 

 as regards its essential descriptive characters by a change in 

 substratum, density of infection or other environmental factor, 

 these characters are worthless for descriptive purposes unless 

 the conditions under which they develop be accurately known." 



And yet mycological journals are still largely filled with these 

 "worthless descriptions," and instead of the collecting of facts 

 and material, mycological nomenclature is increasingly encum- 

 bered with more and more names. 



From what has already been said it must surely be granted 

 that the morphological facies of an organism is not necessarily a 

 constant expression, but that it may vary beyond the recognised 

 limits of the species under the influence of changed environmental 

 conditions. Is such variation sporadic and irregular or does 

 it exhibit a constant and definite relation to particular cultural 

 factors and stimuli? In bacterial investigations of a decade 

 and more ago this question was all important and still 

 unanswered; but with fuller knowledge and more particularly 

 with the ever-increasing refinement of technique it has been 

 demonstrated that the response of bacteria to standardised 

 factors is definite and constant. 



The technique of mycology is still far from perfect for the 

 science is but young, and we cannot as yet answer the ques- 

 tion with an unconditional affirmation. With the exception, 

 however, of some few doubtful results such as those of Shear 



