638 A MANUAL OF THE PENICILLIA 



colony areas; reverse usually in duller shades of red than on Czapek; 

 penicilli as described above. 



Colonies on malt extract agar growing more rapidly, up to 6.0 to 6.5 cm. 

 in two weeks, usually thinner, plane, with surface velvety, tufted or funicu- 

 lose, conidal structures arising almost entirely from the substratum, less 

 abundantly produced in the marginal colony areas; reverse showing red 

 pigmentation in varying amounts, usually most pronounced in central 

 areas; odor slightly fragrant, somewhat suggestive of apples; penicilli as 

 described al)ove. 



Species description centered upon NRRL 1062, isolated in 1930 from 

 "mildew" on currency paper from The Bureau of Printing and Engraving, 

 Washington; and upon NRRL 2120 received in May 1945, from Dr. W. 

 Lawrence White, Philadelphia Quartermaster Depot, as an isolate from 

 cotton duck exposed in Panama. The species is approximated by two 

 strains received in February 1946, from the Centraalbiu-eau as Penicillium 

 crateriforme Oilman and Abbott. These latter strains differ from the above 

 primarily in producing mycelial felts of closer texture on Czapek and steep 

 agars, and in producing longer sterigmata up to 12 to 15/x in length. There 

 is no suggestion on any substrate of crateriform colonies, the character 

 upon which the species name was originally based. 



Penicillium rubrum Stoll, as the species is understood by us, is closely 

 allied to P. purpiirogerium of the same author and is distinguished from 

 the latter species primarily by its smooth- walled conidia; grayish yellow- 

 green rather than dark olive-green conidial areas; and the production of 

 more or less red pigmentation in colony reverse on malt agar. Individual 

 strains are encountered which completely bridge between the two species, 

 and it is possible that they should be regarded as representing different 

 aspects of the same species. 



Like Penicillium purpurogenum, P. rubrum appears to be widely dis- 

 tributed in nature and may be isolated from soil or from various organic 

 materials. It has been repeatedly isolated from moist paper stocks and 

 from exposed fabrics subjected to weathering. Under such conditions, its 

 presence is usually revealed by the development of conspicuous areas of 

 red or reddish discoloration in the substrate. 



Individual strains as isolated show considerable variation in rate of 

 growth, colony texture, pigmentation, and to a lesser degree in microscopic 

 details, yet obviously constitute members of a single species aggregate. 

 NRRL 2123, isolated from cotton duck exposed in Florida, and submitted 

 for identification by Professor Wm. H. Weston, is apparently characterized 

 by an invertase deficiency. The strain develops in a manner characteristic 

 of the species on media containing dextrose, but grows very sparsely and 

 sporulates lightly upon all media containing sucrose as a source of carbon, 



