174 A MANUAL OF THE PENICILLIA 



cillate but showing an occasional branch; sterigmata in crowded clusters 

 numbering 10 to 12 or more in the verticil, mostly 8 to 12/i by 3.0 to 3.5/i 

 (fig. 49D), commonly producing chains of conidia in fairly well-defined 

 columns up to 150^ or more in length, sometimes splitting in age, in other 

 strains showing conidial chains only loosely parallel; conidia globose to sub- 

 globose, comparatively thin-walled, smooth or finely roughened, mostly 3.0 

 to 3.5m in diameter. 



Colonies on steep agar slightly larger than on Czapek, zonation reduced 

 or lacking, velvety, radiately wrinkled, Avith texture as described above, 

 heavily sporing (fig. 49B), c^uickly developing blue-green shades (see 

 above), color in reverse deeper and somewhat more intense than on 

 Czapek, with purplish tints more pronounced; penicilli as described above 

 but with conidial chains in columns up to 200 to 300^ long. 



Colonies on malt extract agar still larger, deeper and darker blue-green 

 in color, almost plane, with traces of zonation at margin; reverse in dull 

 dark brown shades; penicilli as on Czapek and steep agars but with coni- 

 dial columns commonly up to 400 to 500/x in length, massed in a close 

 stand and often breaking away when the culture dish is tapped. 



Species description centered upon strains NRRL 1915 from George 

 Smith, London School of Hygiene and Tropical Medicine, as No. Ad 6, 

 labeled Penicillium frequentans; NRRL 1917 and 1918, from the same 

 source as P. frequentans, designated No. Ad 67 and No. Ad 69 respectively; 

 NRRL 763 from Z. I. Kertesz as a pectinase producer; and many addi- 

 tional strains similar in cultural appearance and in details of morphology. 

 This species occurs in soil and upon decaying vegetable matter, and repre- 

 sents one of the most abundant and widely distributed of all the Penicillia. 

 Westling's name is exceedingly appropriate. 



In Penicillium frequentans, as in other widely distributed species of 

 Penicillium, individual strains show appreciable variation in gross colony 

 appearance and in the finer details of morphology. Gradations, however, 

 are regularly encountered with the result that such variants do not stand 

 apart as forms clearly separable, but rather seem to represent different 

 aspects of an abundant and variable species. For example, strains are 

 commonly isolated which show little or no roughness either of conidia or 

 conidiophores and probably represent the basis of P. glabrum (Wehmer) 

 Westling (see p. 176). Other isolates consistently show a limited rough- 

 ness of conidia and commonly of conidiophores as well, and one of this 

 type may have served as a basis for P. jlavi-dorsum Biourge in which stalk 

 and sterigmata walls were reported as squamulose (see p. 176). Limited 

 variations in color also occur, with individual strains showing the range 

 indicated in the description above. Almost invariably, strains of deeper 

 green color produce conidia with walls definitely roughened. 



