ASYMMETRICA-VELUTINA 385 



greatly increased, reaching at times 40 per cent of the sugar employed. 

 Oxalic acid so produced was not an end product but reached a maximum 

 in eight to twelve days and then diminished. Penicillium oxalicimi pro- 

 duced acid from sucrose, lactose, and potato starch. 



Sinha (1946) reported Penicillium atramentosimi to be one of several 

 molds causing a decay of mangoes in the United Provinces. 



Penicillium digitatum Series 



("Green Rot" of Citrus Fruits) 



Outstanding Characters 



Colonies on Czapek solution agar growing very thinly and very restrictedly, 

 characterized by a limited submerged vegetative mycelium bearing com- 

 paratively few and very irregular, asymmetric penicilli. 



Colonies on steep and malt agars growing luxuriantly, spreading broadly, 

 loose-textured, velvety or nearly so, fairly heavy sporing in dull yellow- 

 green shades, becoming grayish olive in age; odor pronounced, strongly 

 aromatic, variously described as suggesting decaying citrus fruits or un- 

 fermented dill pickles. 



Conidiophores coarse, comparatively short, arising from submerged hyphae 

 or from the basal mycelial felt, smooth-walled. 



Penicilli asymmetric, very irregular in size and pattern, with identity of 

 branches and metulae often poorly established, bearing sterigmata and 

 conidial chains at various levels in the penicillus. Cellular elements 

 usually large, coarse, and irregular. 



Conidia at first cylindrical, usually becoming elliptical or occasionally sub- 

 globose, extremely variable in size but larger than in almost any other 

 series. 



Typically produces an olive green rot of citrus fruits. Rarely observed 

 upon or isolated from other substrata. 



The series is represented by a single species, Penicillium digitatum Sacc, 

 which is responsible for serious losses of citrus fruits in commerce. In its 

 natural habitats (figs. 103 A and B), this mold produces an olive-colored rot 

 characterized by the presence of a dense, powdery layer of olive-colored 

 conidia. Growth on citrus fruits is very rapid, and starting from small 

 localized infections, the molds can completely cover the surface of an orange, 

 lemon, or even a large grapefruit within 3 to 4 days at 20 to 24°C. Such 

 fruits, when exposed to the air, dry up rapidly, shrink in size, and eventually 

 become hollow, mummified shells, dull olive-brown in color. Members of 

 the P. italicum series (pp. 523-531), on the other hand, as they infect citrus 

 fruits, produce blue-green conidial masses in greater or less abundance and 



