ASYMMETRICA-VELUTINA 373 



his type strain, discussed by Thorn in 1930 as No. 4733.22 and now maintained as 

 NRRL 841, represents a comparatively deep, rather flocculent, medium sporing mem- 

 ber of the P. chrysogenum series which is regarded as approximating P. cyaneo-fulvum 

 Biourge. Conidia are comparatively large and somewhat elliptical, and colonies on 

 Czapek's agar produce abundant yellow exudate and bright yellow pigments in re- 

 verse. A culture received from the Centraalbureau in February 1946 as P. hrunneo- 

 rubrum Dierckx from Biourge in 1929, and probably from the same original source as 

 NRRL 841, differs from it in producing heavier sporing colonies that are light blue- 

 green in color with limited clear exudate and reverse almost colorless. In this, as in 

 many other cultures long maintained in laboratory culture, there is evidence of 

 marked variation. 



Penicillium citreo-roseum Dierckx (Soc. Scien. Brux. 25: 86. 1901; in Biourge, 

 Mongr., La Cellule 33: fasc. 1, pp. 182-184; Col. PI. IV and PI. VII, fig. 38. 1923; 

 Thorn, The Ponicillia, pp. 265-266. 1930) as known from Biourge's description and 

 his type strain, reported by Thom in 1930 as No. 4733.36 and now maintained as NRRIv 

 834, is regarded as approximating P. cyaneo-fulvum Biourge. Cultures are compara- 

 tively deep, medium sporing, light blue-green in color, produce abundant light straw 

 colored to pale amber exudate, and colony reverse in yellow to golden yellow shades. 

 A strain received from the Centraalbureau in February 1946 as a culture of P. citreo- 

 roseum Dierckx from Biourge (in 1937) essentially duplicates NRRL 834 except for 

 reduced exudate formation. Biourge's concept of Dierckx's species appears to have 

 been based upon a strain which developed reddish colors in the colony surface and 

 reverse, and Thom in 1930 noted the reverse as "yellow then slowly red in center." 

 Neither the strain maintained at this Laboratory nor that from Baarn now. exhibit 

 this distinguishing characteristic. There appears to be no other basis for separating 

 it from other more or less flocculent, light to medium sporing strains that are pale 

 blue-green or gray in color and produce globose to subglobose conidia. These are 

 regarded as representing or approximating P. cyaneo-julvum Biourge. 



Occurrence and Significance 



Members of the Petiicillium chrysogenum series regularly occur in soil and 

 are commonly found upon a wide variety of organic substrata, including: 

 cheese and other dairy products, bread and pastries, fruits, vegetables, 

 meat and meat products, improperly canned foods, and decaying vegetation 

 of all kinds (Raper, Alexander, and Coghill, 1944). Representative cul- 

 tures have come from every region from which either cultures or materials 

 have been examined. The species assigned here are unquestionably world- 

 wide in distribution. 



Principal interest in this series stems from the capacity of these molds to 

 produce the antibiotic penicillin. Since so much work has been done on 

 this fermentation during the past few years, and since so many papers have 

 been published, we have included a separate chapter covering the history, 

 significant developments, and present status of this fermentation (see 

 Chapter V). 



Since molds belonging to the Penicillium chrysogenum series are unusually 

 abundant in nature it is neither surprising that they are commonly assq- 



