ASYMMETRICA-VELUTINA 393 



Conidiophores conspicuously roughened or tuberculate in aerial portions, 

 with cellular elements of the penicillus often similarly roughened. 



Penicilli asymmetrical, irregularly branched, bearing conidia in long tangled 

 chains or adherent in loose columns. 



Conidia comparatively heavy-walled and smooth, appearing dark yellow- 

 green when viewed under high magnifications. 



. Series Key 



2. Conidiophores typically rough-walled; colony margins usually appearing arach- 

 noid P. roqueforti series 



a. Colonies broadly spreading, with surface plane or nearlj^ so, margins thin, 



typically appearing arachnoid P. roqueforti Thom 



b. Colonies restricted, strongly wrinkled or furrowed, margins hardly arachnoid. 



P. casei Staub 



Members of this series are the predominant molds in the whole group of 

 cheeses characterized by streaks, or "marbling", of green mold (fig. lOoA). 

 Closely related strains appear in the true Roquefort, or sheep's milk cheese 

 of southern France, in the "fromages bleus" of central France, made from 

 either sheep's milk or cow's milk, in Gorgonzola as made in northern Italy, 

 in Stilton as made in England, in Gammelost as made in Norway, in Blue 

 cheese or American Roquefort as made in the United States, and in many 

 less well-kno^^'n varieties of loose-textured cheeses which obtain their char- 

 acteristic flavor and appearance from the molds which line the channels and 

 cracks throughout their mass. Members of this series are likewise the 

 dominant molds found in spoiling ensilage, and appear fairly frequently in 

 miscellaneous cultures from food products and soils. 



In contrast to the Camembert type cheese molds, which are deeply floc- 

 cose, white or nearly so, and grow only on the surface of the pressed milk 

 curd, members of the Penicilliuyn roqueforti series represent velvety, dark 

 green forms which invade the holes and cracks in loose-textured cheeses. 

 In manufacturing such cheeses as Roquefort, Gorgonzola, Stilton, etc., the 

 curd is so managed as to leave cracks, channels and openings between the 

 particles as they are pressed together. The "marbling" characteristic of 

 such cheeses when ripe results from the growth and sporulation of the mold 

 throughout the network of interconnecting channels. In studying these 

 cheeses, Thom and Currie (1913) showed that these channels and spaces 

 within the cheese contained less ox3^gen than atmospheric air, and that the 

 Roquefort mold dominated the flora of these spaces because of its ability to 

 grow in gas mixtures containing as little as 5 per cent oxygen. 



Members of the Penicillium roqueforti series, as it is now understood, have 

 been studied particularly with relation to their role in cheese manufacture. 



