492 A MANUAL OF THE PENICILLIA 



either as overgrowths or in the form of sectors is not uncommon. Such 

 variants can usually be perpetuated in culture, and often continue to ex- 

 hibit differences equal to those observed between new isolates. 



Resulting in part from strain individuality and natural variability 

 among these forms, and in part from an apparent lack of appreciation of 

 the materials examined by others, many different species, obviously closely 

 related, have been described by different investigators working in different 

 localities and generally at different times. The type strains of some of 

 these species have been preserved and were available for the present study. 

 Certainly some of the described species cannot be regarded as valid, while 

 the selection of those which should be so considered must of necessity be 

 somewhat arbitrary. We have endeavored to select those species which 

 through common usage have become best recognized. 



Based upon the sum of our observations and a re-examination of original 

 descriptions and figures, we believe the series can be best subdivided into 

 species, or species aggregates, centering around Penicillium cyclopium 

 Westling, P. puberulum Rainier, P. martensii Biourge, and P. aurantio- 

 virens Biourge. Cultures are encountered which do not fit completely 

 either of the species presented here, but it is believed that separation along 

 the lines proposed will differentiate between the vast majority of strains. 

 To recognize additional species or to make the descriptions more restric- 

 tive would, it is believed, place unwarranted emphasis upon variation be- 

 tween individual strains. On the other hand, to recognize only a single 

 species, P. cyclopium, would necessitate the preparation of a description 

 which would have to be inclusive almost to the point of being meaning- 

 less. 



PeniciUmm cyclopium Westling is the most abundant and the most 

 characteristic species in the series. Typically it is characterized by colonies 

 showing limited to pronounced faseiculation of conidiophores, a dull blue- 

 green coloration, and other features as indicated in the series characters 

 above. Strains vary materially, and isolates are encountered which merge 

 imperceptibly into the other member-species. The globose, rough conidia 

 of P. cyclopium var. cchinulatum are regarded as sufficiently distinctive to 

 warrant the description of this new variety. Penicillium puberulum 

 Bainier is hardly fasciculate but possesses so many characteristics (cultural, 

 morphological, and physiological) in common with P. cyclopium that it is 

 placed here irrespective of colony surface and texture. In its most typical 

 aspect P. martensii Biourge differs in producing colonies of bluer color, less 

 definitely roughened conidiophores, and elliptical conidia. Penicillium 

 auraniio-virens is much like the preceding, but differs from it in producing 

 colonies on malt agar characterized by abundant yellow mycelia and little 

 or no spore production. 



