MONOVERTICILLATA 205 



than the deep bhie-greens of typical P, impUcatum, and colonies in reverse 

 are less deeply colored. Nevertheless, in rate of growth and in the type of 

 colonies developed, the species appears to be closer to P. impUcatum than 

 any other well-recognized form. 



Occurrence and Significance 



Memlicrs of the Penicillium impUcatum series are not infrequently 

 isolated from soil, and have been encountered rather commonly among 

 the Penicillia isolated from fabrics and other types of military ecjuipment 

 undergoing deterioration in the field. Their significance under such con- 

 ditions is largely a matter of conjecture. No biochemical studies are 

 known to have been based upon either of the three species which comprise 

 the series. 



Penicillium decumbens Series 



Outstanding Characters 



Colonies slow-growing usually restricted, superficially appearing velvety 

 or lightly floccose, consisting of networks of trailing and interwoven 

 vegetative hyphae, ranging from comparatively loose-textured in some 

 species to dense, tough mycelial felts in others. 



Penicilli strictly monoverticillate and consistently small, typically borne 

 on short, lateral branches (conidiophores) from trailing, looping or 

 interwoven aerial hyphae, seldom arising directly from the substratum. 



Conidia small, usually somewhat elliptical, about 2.0 to 3.0/i in long axis 

 with walls smooth in most forms, delicately roughened in others. 



Vegetative mycelium delicate, thin-walled. 



Series Key 



2. Colonies appearing velvety or with surface lightly floccose; conidiophores borne 

 primarily as short branches from loosely trailing or compacted vegetative 

 hyphae P- decumbens series 



a. Colonies loose-textured, with margin usually thin and generally consisting of 



a loose network of interlacing hyphae bearing short conidiophores. 



r. Conidial areas in light gray-green shades with reverse uncolored or in yellow 

 drab shades on Czapek agar but becoming cherry red on malt and wort 

 agars P- chermesinutn Biourge 



2'. Conidial areas in dull blue-green shades with reverse usually uncolored on 

 all media P- decumbens Thom 



b. Colonies close-textured, tough, almost leathery, restricted, with margin com- 



pact but showing occasional stolon-like hyphae. 

 1'. Vegetative mycelium yellow, generally characterizing the colony even in 



age, sporulating lightly on Czapek agar P. citreo-viride Biourge 



2'. Vegetative mycelium white, often characterizing the colony when young, 



but developing blue-green conidial areas in one to two weeks, reverse 



uncolored or in light vinaceous gray shades P. fellutanum Biourge 



3'. Vegetative mycelium white to pale vinaceous, sparsely sporulating, reverse 



bright orange-red to maroon P. roseo-purpureum Dierckx 



