170 a manual of the penicillia 



Penicillium frequentans Series 

 Outstanding Characters 



Colonies mostly fast-growing, usually spreading broadly, appearing velvety 



or with surface lightly floccose. 

 Conidiophores erect or ascending, rarely branched, with walls smooth to 



definitely roughened, arising from a basal felt or from trailing, looping, 



loosely interwoven aerial hyphae. 

 Penicilli strictly monoverticillate, comparatively large, with sterigmata 



forming a compact cluster, and with conidial chains usually in loose to 



compact columns. 

 Conidia globose to subglobose, rarely eUiptical, from 2.5 to 5.0Ai or more in 



diameter, and ranging from smooth to coarsely roughened, depending 



upon the species. 



Series Kerj 



1. Colonies velvety or nearly so, with conidiophores arising mostly from the sub- 

 stratum, 

 a. Colonies generally spreading broadly on most media. 



1'. Conidia globose to subglobose P. frequentans series 



aa. Colonies with conidial areas strictly velvety and with reverse usually 

 in orange-brown to reddish purple shades. 

 1". Conidia mostly 2.5 to 3.5/;, with walls thin, smooth or finely rough- 

 ened P. frequentans Westling 



2". Conidia mostly 4.0 to 5.0/^, with walls heavy, dark green, and 



coarsely roughened P. purpurrescens (Sopp) n. comb. 



bb. Colonies with conidial areas strictly velvety and with reverse usually 



in bright orange-red to red shades P. multicolor G.-M. and P. 



(see P. implicatum series, p. 196) 



cc. Colonies with surface loose-textured, with conidial structures arising 



from the substratum and from aerial mycelia, and with reverse un- 



colored, pinkish, or in purplish drab shades. . . P. spinulosum Thom 



Members of this series are among the most widely distributed and the 

 most abundant of all the Penicillia and many species assignable here have 

 been described by different authors. Specific diagnoses have been based 

 upon particular cultural or structural characteristics believed to be unique, 

 less commonly upon the substrata from which the molds were first isolated. 

 As would be expected in a series so abundant, marked variation between 

 strains is regularly encountered. Viewing the series as a whole we believe 

 it can best be separated into three reasonably well defined species aggre- 

 gates centering around Penicillium frequentans Westling, P. purpurrescens 

 (Sopp) n. comb., and P. spinulosum Thom (fig. 48). Each species aggre- 

 gate is characterized by considerable variation within itself, and strains are 

 not infrequently encountered which tend to bridge the hues of separation 



