576 



A MANUAL OF THE PENICILLIA 



regularities (fig. 145D and E), distinctively pale orange or tan in mass, 

 very pale yellow when viewed singly. Spores mature in 10 to 14 days at 

 45°C., and will germinate without special treatment within 24 hours at 

 45°C., the two valves of the wall separating. 



Colonies on Czapek solution agar growing less rapidly, very thin, floccu- 

 lent, attaining a diameter of 4.0 to 5.0 cm. in 10 to 12 days at 45°C., re- 

 maining white longer, but at length becoming pale lavender, cinnamon 

 pink, or avellaneous but usually not showing grayish green shades from 

 developing conidia. 



Colonies on steep agar closely approximate those on glucose-yeast agar 

 in rate of growth, texture, color, and in the abundance of conidium pro- 

 duction. 



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r;N 4? 



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Fig. 146. Penicillium duponti Gr. and M;iub. emend. Emerson. ,4 , Nearly mature 

 perithecia on chopped guayule shrub incubated 14 days at 45°C., X 9. B, Mature 

 perithecia dissected out, X 9. C, Cross section of nearly mature perithecium show- 

 ing plectenchymatous peridium and fertile cavity filled with asci and ascospores, 

 X 150. (Photographs by Louis C. Erickson for Ralph Emerson.) 



On chopped guayule shrub, growth is at first white, delicate, cottony, 

 then becoming pale gray to yellowish green with the start of conidium- 

 formation, and in age dark mouse gray with a greenish cast. White knots 

 of hyphae begin to be very conspicuous in 4 or 5 days at optimum tempera- 

 tures and subsequently develop into the pale gray perithecia that charac- 

 terize the species (fig. 146). 



A similar but generally somewhat delayed development of conidial struc- 

 tures and perithecia occurs in deep cultures of sterilized cracked or rolled 

 oats. 



Species isolated originally by Griffon and Maublanc from fresh manure 

 which "heated naturally" and from wet hay in an incubator at 50°C. Subse- 

 quently isolated by Emerson as follows: "Origin: Self -heated, retting 



