ASYMMETRICA-FASCICULATA 489 



mostly 3.5 to 4.0m in diameter but ranging up to 4.5 or even 5.0/x, with walls 

 comparative!}^ heavy, smooth or nearly so. 



Colonies on steep agar growing more rapidly, attaining a diameter of 

 5.0 to 5.5 cm. in 12 to 14 days, but essentially duplicating the above in 

 pattern, texture, and color; penicilli as described above. 



Colonies on malt agar 4.0 to 5.0 cm. in 12 to 14 days, comparatively thin, 

 heavily sporing, plane (fig. 125F), except for a slight flocculent overgrowth 

 in colony centers, marginal areas appearing granular, approximately sage 

 green (R., PL XLVII) to Russian green (R., PI. XLII) with reverse in dull 

 peach shades; penicilli as on Czapek agar but generally showing less ir- 

 regularity in branching. 



Species description centered upon NRRL 966 isolated in the summer 

 of 1940 as a laboratory contaminant in Washington, D. C, and diagnosed 

 as Penicillium palitans. The species is also represented by NRRL 2033 

 received in May 1946, from the Centraalbureau as a strain of P. palitans 

 originally from Westling; NRRL 1164, from G. A. Ledingham, Ottawa, 

 Canada, in 1940, as an isolate from pulp-mill waste; and three cultures 

 under this name received in July 1947 from George Smith, London School 

 of Hygiene and Tropical Medicine as strains studied by Birkinshaw and 

 Raistrick (1936). NRRL 914, an isolate from pears, received in 1939 

 from Professor Heald, Pullman, Washington, approximates the species. 



The strain received from the Centraalbureau as Penicillium palitans of 

 Westling probably represents the type culture. It is, however, somewhat 

 looser in texture than most strains believed by us to represent this species. 

 Our description above is written in broad enough terms to include West- 

 ling's strain, together with thinner- and closer-textured strains such as 

 NRRL 966 and 1164. The penicilli in all of these cultures are identical. 



Penicillium palitans is believed to be closely related to P. viridicatum, 

 hence is included in the series with it. It differs from the latter species, 

 however, in producing colonies which are typically darker yellow-green, 

 often less fasciculate, and show conidia usually larger. Certain strains 

 believed to represent the species show characteristics which suggest P. cy- 

 clopium Westling. 



While Penicillium palitans is assigned in the P. viridicatum series, largely 

 upon the color of conidial areas and the character of its conidial structures, 

 many strains fail to show definite fasciculation. The colony surface of all 

 strains, however, may be regarded as "mealy". Placement here seems to 

 be more logical than elsewhere. 



Occurrence and Significance 



Penicillium viridicatum and allied species commonly occur in soil. From 

 their distribution and number, they are assumed to play an active role in 

 the slow aerobic decomposition of organic residues. 



