BIVERTICILLATA-SYMMETRICA 631 



or red shades, and massed conidial structures, deep yellow-green to gray- 

 green in color; reverse typically in deep cherry red or purplish red shades, 

 with the surrounding agar usually colored in similar but lighter shades. 



Conidiophores commonly arising from the basal felt or from submerged 

 hyphae in thin colony margins; with walls smooth or roughened depend- 

 ing upon the species and strain. 



Penicilli typically biverticillate and symmetrical, usually consisting of a 

 simple verticil of metulae, which in turn bear compact clusters of parallel 

 or somewhat divergent sterigmata, depending upon the species and strain. 



Conidia usually elliptical, but ranging through subglobose to strictly glo- 

 bose; with w^alls variable, often somewhat roughened, but ranging from 

 smooth in some species to conspicuously echinulate in another. 



Odor usually pronounced, often aromatic or fragrant, commonly suggesting 

 apples or walnuts in cultures on malt agar. 



Series Key 



a. Colonies on Czapek and steep agars usually developing an intense red or purple- 

 red pigmentation; commonly producing aromatic odors suggesting apples or 



walnuts on malt agar P. purpurogenum series 



1'. Colonies consistently producing deep red colors in reverse; surface usually 



heavy sporing and showing an evident but limited development of yellow or 



orange-red aerial hyphae. 



aa. Conidia elliptical to subglobose; penicilli comparatively long, sterigmata 



closely parallel; pigmentation diffusing throughout the surrounding 



agar. 



1". Conidia typically roughened; colonies sometimes spreading; conidial 



areas in dark yellow-green shades P. purpurogenum Stoll 



aaa. Producing sclerotia, at least when newly isolated. 



P. purpurogenum var. rubri-sclerotium Thom 

 2". Conidia smooth; colonies more restricted; conidial areas in lighter 



yellow-green to gray -green shades P. rubrum Stoll 



bb. Conidia globose, echinulate; penicilli comparatively short; sterigmata 

 somewhat divergent; pigmentation seldom diffusing throughout the 



surrounding agar P. aculeatum Raper and Fennell 



2'. Colonies developing red-orange, yellow-orange or greenish brown rather than 

 deep red colors in reverse; surface usually characterized by prominent areas 

 of sterile yellow aerial mjxelium P. variabile Sopp 



This series includes some of the most colorful members of the genus 

 PenicilUum. With the exception of a single species, P. variabile Sopp, all 

 members of the series are characterized by the production of intense red or 

 purplish red pigments on Czapek and steep agars. Pigmentation is es- 

 pecially pronounced in the colony reverse, but in most forms diffuses quite 

 generally throughout the entire substratum and often colors the vegetative 

 mycelium in similar and characteristic shades. 



