528 A MANUAL or THE PENICILLIA 



of conidia; conidia at first typically cylindrical but becoming definitely el- 

 liptical or even subglobose at maturity (fig. 133B), dimensions extremely 

 variable but generally 4.0 to 5.0m by 2.5 to 3.5/x, with individual spores 

 when elliptical ranging up to 9.0 by 5.0^ or 6.6^ when subglobose, walls 

 smooth, appearing pale yellow-green in mass. 



Colonies on steep agar spreading broadly, attaining a diameter of 5.0 

 to 6.0 cm. in 10 to 12 days at room temperature, plane except for shallow 

 radial furrows, heavily sporing, generally in glaucous gray shades (R., PL 

 XLVIII), with surface usually appearing granular or tufted throughout 

 and with marginal areas commonly showing prominent f asciculation ; odor 

 less pronounced but essentially as on Czapek ; no exudate produced ; reverse 

 at first in dull yellowish shades but soon darkening, and in mature colonies 

 often showing dark to blackish coloration in radiating lines or sectors; 

 penicilli essentially as described above but commonly larger than on 

 Czapek. 



Colonies on malt extract spreading broadly, 5 to 6 cm. in 10 to 12 days 

 at room temperature, typically plane, heavily sporing (fig. 135B), with 

 entire colony often appearing coarsely granular from the abundant de- 

 velopment of clustered conidiophores; odor as described above but often 

 less marked ; no exudate ; reverse in dull yellow-brown shades with blackish 

 sector-like areas often conspicuous; penicilli comparatively "stocky" and 

 showing great variation in the dimensions of parts but generally exhibiting 

 the pattern described on Czapek; conidia show great variation in size and 

 shape, with individual cells commonly up to 7.0m or more in long axis. 



Individual strains may vary appreciably in the degree of fasciculation 

 shown and in their general rate of growth. Some grow rapidly and fill 

 the entire agar plate or tube, others are more restricted and seldom exceed 

 3.0 to 4.0 cm. in diameter on Czapek agar even after three or four weeks. 

 All grow more luxuriantly upon malt extract and steep agars; and on 

 Czapek there is some evidence that many strains suffer from a limited 

 nutrient deficiency. Particular isolates often show considerable intra- 

 strain variation, and it is commonly possible to isolate from a single culture 

 difterent substrains which show marked variation in rate of growth, amount 

 of sporulation, general colony texture and color, and in the abimdance 

 and size of fascicles or coremia produced. It thus becomes somewhat 

 difficult to describe the species in tangible terms and yet make such a diag- 

 nosis sufficiently general to embrace all of the strains belonging in it. 



Cultures long maintained upon laboratory media commonly show pro- 

 gressively lighter sporulation, which may be accompanied by a decreased 

 pathogenicity. Members of this series are comparatively short-lived, 

 and cultures should be re-transferred at comparatively frequent intervals 

 to insure viability. New isolates, however, can almost always be secured 

 at the nearest fresh fruit market and stocks can be easily replenished. 



