USE OF THE MANUAL 119 



less these clearly failed to represent the original concept, in which case 

 some more recent isolate, or isolates, regarded as truly representative was 

 selected for this purpose. We have had available for this study a wealth 

 of living material (see pp. 87-88), including the types of many, if not an 

 actual majority, of the species considered. Type material has often been 

 available for both the species recognized and others reduced to synonymy. 

 It has perhaps been the detailed observation of such types as often as the 

 analysis of published descriptions which has governed our decisions regard- 

 ing species recognition on the one hand and synonymy on the other. 



Species that are not recognized as valid have been handled in one of two 

 ways. If the species is represented in culture collections by named speci- 

 mens, or if it has been reported in the literature fairly commonly, it is dis- 

 cussed in a short paragraph following the species with which it is regarded 

 as probably synonymous. Specific reasons for our course of action are 

 usually cited. If the species was not originally described in tangible terms, 

 and if it has not been generally accepted or reported in the subsequent 

 literature, it is listed only in the Species Index at the end of the Manual 

 (Chapter XVIII). Our opinion, if any, as to the probable relationship or 

 synonymy of the species is given there. 



Keys 



The number of recognizable species of Penicillium is too large for all of 

 them to be conveniently included in a single key. Furthermore, in tracing 

 the identity of any given strain or culture we believe that it is neither neces- 

 sary nor desirable to handle large portions of a key which are irrelevant to 

 the task in hand. For this reason, we shall introduce here only general 

 keys to the major subdivisions of the genus and to the series which comprise 

 them. Once the suspected series relationship of the unidentified culture 

 is decided upon, the user can quickly determine the probable correctness 

 of such placement by examining (1) the list of "outstanding characters" 

 and (2) the series key, both of which appear at the beginning of each series 

 discussion. 



The first key is presented in diagrammatic form (fig. 33) and is designed 

 to enable the worker to quickly determine the probable broad relationships 

 of his Penicillium. Space limitations prevent us from including in such a 

 key much information of real diagnostic value, hence it will oftentimes prove 

 inadequate and indecisive. Under these conditions the user should imme- 

 diately go to the written "General Key to Series" which follows, and if 

 necessary to the more detailed keys which introduce the various sections 

 and sub-sections. Despite its recognized shortcomings, the diagrammatic 

 key is presented in the belief that it will generally facilitate identifications. 



The second key, or the "General Key to Series," is presented in conven- 



