18 GENERA OF FUNGI 



Orders and Families 



The definition and limitation of the orders and famiHes of fungi is 

 necessarily more uncertain than in the case of genera. In consequence, it is 

 inevitable that mycologists should differ widely in their treatment of these 

 groups. This is especially marked in the case of the Ascomycetes, where 

 for example Hoehnel would place the MicrotJiyriaccae and Trichothyriaceac 

 in the Perisporialcs, while Theissen and Sydow include them in their Heiui- 

 sphacrialcs. Such differences usually arise from divergent views as to the 

 importance of criteria and from lack of knowledge of life-histories and 

 comparative morphology. They also spring from the fact that the complex 

 interrelations of many groups permit placing certain genera with about equal 

 propriety in either of two families or orders, as well as from the lack of 

 uniformity in many genera. Thus, Physalospora and Botryosphaeria are 

 by some referred to Sphacriaceae and by others to Dothideaceae, while 

 Mclanospora, in which the type possesses gray membranous perithecia 

 though this is black and subcarbonous in others, may be placed with almost 

 equal warrant in either Hypocrcaccac or Sphacriaceae. In many groups no 

 definite and fixed boundaries exist, and unusual or atypical genera must be 

 sought in more than one place. 



It is inevitable that the multiplication of genera on insufficient knowl- 

 edge and unreliable characters or on vague and trivial ones, should be 

 reflected in the splitting of long-established orders and families. This rarely 

 represents any new knowledge, nor does it advance the understanding of 

 such groups. It constantly shifts the foundations of mycology to the disad- 

 vantage of practically every one, and constitutes one of the subjective 

 processes unfavorable to the realization of a sound and scientific basis for 

 mycology. To follow a conservative course in the recognition and limita- 

 tion of orders and families seems to us to best serve the purpose of the 

 present book and the interests of its users. 



The Natural System 



The system employed in the present book constitutes an endeavor to 

 approximate the natural system in several respects. It appears obvious that 

 there is but one natural system and equally evident that any approach to it 

 is the result of the work of many minds. Hence, in spite of its convenience 

 for reference, it is more or less inexact to give the name of an individual to 

 any particular arrangement. Phylogeny still labors under the handicap of 

 being regarded by many as a labyrinth of personal opinions, and until it is 

 generally recognized that it affords an inviting field for experiment and 

 investigation quite as much as any other, no great progress in it can be 

 expected. 



At present, considerations of space permit reference to but two or three 

 basic principles that have been observed in the arrangement of orders and 

 families. The first of these is that the fungus is a physiological adjustment to 



