VIU PREFACE 



cumulated by him at Storrs, Connecticut, and subsequently in the various 

 laboratories in Washington which came under his direction, were trans- 

 ferred to Peoria. The Collection so established at the Northern Labora- 

 tory has been enormously increased during the past eight years by the 

 isolation of new materials from many natural substrates, by the contribu- 

 tion of cultures by many collaborators, and finally through the cooperation 

 of Dr. Johanna Westerdijk who, in 1946, contributed transfers of all of the 

 Penicillia in the Centraalbureau at Baarn. 



The first obligation of a monographer of the Penicillia is t<^ report as 

 truly as possible what his predecessors described under particular names. 

 His ideal is to produce as complete and as faithful a presentation as pos- 

 sible of the work of his predecessors, supplemented by his own observations 

 and knowledge. In contrast to the monographer, the writer of a manual 

 of the Penicillia must begin with the establishment of a genus concept, 

 then account for all species that have been assigned to it. He may cor- 

 rect, redescribe, reassign, or reduce to synonymy any specific name and 

 description encountered, so long as his own descriptions lead to the identifi- 

 cation of actual material, and to the assignment to that material of Latin 

 names which are correct according to accepted rules of nomenclature. 

 His primary obligation is to the investigator who needs to identify an 

 oiganism. The manual must, in addition, furnish such guides to the 

 literature as will permit the critical worker to search original sources for 

 himself whenever he requires more detailed information than the manual 

 supplies. 



With this background and philosophy, the preparation of this Manual 

 was undertaken. The monographic feature of Thom's earlier work (1930) 

 has been dropped. The concept of series, i.e., groups of strains having 

 fairly consistent morphology and usually showing related biochemical 

 activities, is emphasized. Within each series, recognized species are ar- 

 ranged in what we consider to be a logical sequence, and the reasons for 

 their recognition are indicated. The punctilious systematist will find 

 that the description of a species of Penicillium is no longer a "photograph- 

 like" presentation of the first strain, or type, as found, but represents in- 

 stead a composite of characters selected as the result of continued cul- 

 tivation of many strains. Such a concept is sufficiently broad and elastic 

 to include the usual range of variants which the experienced worker will 

 naturally expect. At the same time, we have attempted to establish 

 species limits with sufficient clarity to exclude forms which are unrelated, 

 and forms which may present only superficial evidence of relationship. 



This Manual is designed primarily as a means for identifying Penicillia 

 which may be encountered in the laboratory, or which for some reason 

 may be significant in microbiological or biochemical processes. It is 



