INTRODUCTION 5 



publication is made in well-known and widely distributed journals, prefer- 

 ably such as are devoted to fungi. The second duty is to insure that copies 

 of all such papers are sent to the chief mycological centers, such as Berlin, 

 London, Paris, Vienna, and Washington, for example. This should also 

 involve the deposition of co-types of all new genera and species in the 

 herbaria at such centers, to facilitate the labors of future students of the 

 group. 



In the hope of furthering the work of mycologists and pathologists the 

 world over, it is definitely planned to issue a new edition of the present book 

 at intervals of three to five years, depending somewhat upon the amount of 

 material that requires attention. In addition to incorporating new and valid 

 genera and determining synonyms, this will also take account of the general 

 progress in the field of systematic mycology. Constructive criticism, both in 

 general and in particular, will be welcomed and utilized, as w^ell as other 

 suggestions designed to render the book more serviceable. 



Criteria 



Since the validity of genera rests upon the value of the criteria 

 employed, it is desirable to pass these in review at the outset. As the criteria 

 necessarily differ in the various groups, their consideration will be restricted 

 chiefly to the Ascomycetes and Deuteromycetes, in which evolution has 

 been most active and the number of genera by far the largest. Moreover, 

 most of the new genera proposed during the past two decades belong in 

 these two groups. As a consequence, the application of criteria here has 

 been fairly consistent and uniform, and thus furnishes a proper basis for 

 e.xamination. 



At present no objective basis exists for the evaluation of criteria and 

 no adequate one is possible until statistical and experimental methods have 

 come more into vogue. Though it is usually assumed that cultural studies 

 yield conclusive evidence as to development and structure, this is not neces- 

 sarily true. On theoretical grounds, the life-history of a fungus should be 

 the same in culture and in nature only when the essential factors are alike, 

 a condition often absent and in most cases extremely difficult to attain. 

 Evidence already available indicates that the results obtained in culture may 

 depart widely from the behavior exhibited in nature, the recent study of 

 Cristidariella by Bowen furnishing a striking example of this (1930). The 

 cultural and natural form differ so much as to warrant placing them in 

 separate genera, and in other cases the difference may be as much as that 

 between families or orders. In consequence, while experiment must be 

 regarded as the corner-stone of a scientific mycology, the experimental pro- 

 cedure must rest squarely upon a proper combination of nature and culture, 

 reinforced bv thorough-going statistical studies over a wide natural range. 



In the general absence of such studies, it must be recognized that our 

 present utilization of criteria rests upon two subjective processes, namely, 

 observation and usage. However, these constitute a much better basis than 



