402 A MANUAL OF THE PENICILLIA 



than above but of similar pattern; conidiophore walls generally less defi- 

 nitely roughened. 



Colonies on malt agar very restricted, about 1.5 cm. in 2 weeks, velvety, 

 heavily sporing, colored as on Czapek; no exudate; penicilli of the same 

 basic pattern as above but more compact and somewhat coarser, with 

 conidiophores consistently heavier, up to 4.5 to 5.0;u in diameter and very 

 conspicuously roughened. 



Species description based primarily upon NRRL 844, Thom's No. 5056, 

 isolated from Swiss cheese. The species is believed to be widely distributed 

 since representative strains have been repeatedly isolated from brown spots 

 on the rinds of Swiss and other related cheeses. While cultures are not 

 difficult to maintain in the laboratory, they tend to die out more rapidly 

 than many of the Penicillia, hence should be transferred more frequently 

 than most. 



Pemcillium casei Staub shows the general characters of the P. roqueforti 

 series sufficiently to be included here more satisfactorily than elsewhere. 

 It differs from the more common molds of the P. roqueforti tj^pe, however, 

 in producing more restricted and slowly growing colonies and in failing to 

 show the broad arachnoid margin characteristic of that species. The co- 

 nidial structures of the two species are strikingly similar. 



Occurrence and Significance 



The distribution of Penicillium roqueforti in nature is largely determined 

 by its physiological characteristics. It is able to grow under quite acid 

 conditions and in an atmosphere of low O2 concentration. Hence, it com- 

 monly appears in the mycoflora of surface layers in fermenting ensilage, 

 and is the dominant mold found in cheeses of the Roquefort type. Its al- 

 most universal use in the manufacture of the latter products rests, not only 

 upon its ability to grow deep into the loosely pressed curd, but more par- 

 ticularly upon the enzymes which it produces and the flavors that are 

 developed through the action of these upon the fatty and proteinaceous 

 milk constituents. 



Roquefort and other cheeses of the same general type have long been 

 produced in various parts of Europe, and limited studies of a mycological 

 nature were early made by Johan-Olsen (Sopp) in Norway (1898), by 

 Dierckx in Belgium (1901), and by Bainier in France (1907a). Production 

 methods, however, were largely empirical, and the manufacture of high 

 quality cheeses resulted from a combination of unique climatic conditions 

 and the successful establishment of a flora in which the mold now known as 

 Penicillium roqueforti represented the dominant species. 



