358 A MANUAL OF THE PENICILLIA 



Penicillium meleagrinum Biourge, marked by rapidly growing, loose- 

 textured, heavily sporing colonies with conidial areas in bright yellow-green 

 shades, exudate pale or uncolored, reverse in dull yellow to vinaceous or 

 brownish fa^vn shades; penicilli comparatively large and often rebranched; 

 and conidia comparatively large and elliptical. 



Penicillium notatum Westling, marked by heavily sporing, velvety col- 

 onies, often appearing close-textured; penicilli smaller than above, com- 

 monly consisting of a single verticil of metulae; conidia globose to sub- 

 globose, usually smaller in size. 



Penicillium cyaneo-fulvum Biourge, marked by less heavily sporing col- 

 onies that are deeper and of looser texture, light blue-green to gray-green 

 in color, exudate and colony reverse often in light yellow shades; penicilli 

 variable in size and pattern and often irregular; and conidia globose to sub- 

 globose, variable in size, in some strains comparatively large up to 4.0^^ or 



more. 



This latter species is recognized to include a number of loose-textured, 

 lightly colored forms which produce pale or limited exudate, and generally 

 show reduced pigmentation in colony reverse and in the surrounding agar. 

 It is possible that such forms may appear as cultural variants of Penicillium 

 notatum or P. chrysogenum. Whatever their origin, several of them have 

 been held as laboratory cultures for many years. Forms of this type are 

 isolated from nature with sufficient frequency to necessitate recognition 

 of a species to which they can be assigned. 



It is clearly recognized that workers in the laboratory will often encounter 

 difficulties in assigning particular strains to one or the other of the above 

 species, for cultures showing the character of more than one "species" are 

 repeatedly encountered. Individual cultures when grown side by side in 

 cultures often show marked differences in gross appearance, only .to have 

 such distinctions slip away and blend into the picture of a variable and in- 

 constant series when great numbers of strains are examined. Further- 

 more, the same strain may show marked differences in habit, texture, and 

 coloration depending upon the particular substratum and other specific 

 factors of environment. Speaking of the type strain of Penicillium chryso- 

 genum (Thorn's No. 26— NRRL 807) Thom, in 1930, wrote as follows: 



"Re-examination of records of observations over the twenty -two years this species 

 has been kept in culture shows as great a range in color in the various recorded experi- 

 ments as is shown by the whole series of Radiata." 



An additional twenty year study of this and other cultures has tended to 

 enhance the significance of this observation. Nevertheless, specific stains 

 generally do possess definite individuality, either cultural, morphological, 

 or physiological in character. These, the experienced mycologist or micro- 



