ASYMMETEICA-FASCICULATA 509 



1'. Conidiophores comparatively long, often up to 500/x or more in ength, with 

 walls smooth or finely roughened; conidia abundant but usually not forming 

 definite crusts -P. expansum (Link) Thorn 



2'. Conid'ophores usually shorter, with walls conspicuously roughened; conidia 

 often forming definite crusts which break away when culture tube or dish 

 is tapped P- crustosuin Thom 



The present series is typified by one of the oldest and best kno^vn species 

 of Penicillivm, namely: Penicillium expansum. This species was de- 

 scribed by Link in 1809 in his ''Observationes," and with P. glaucum and 

 P. candidum constituted the three species upon which Link established his 

 genus Penicillium.. He reported P. expansum to be common upon rotting 

 fruits, which in Germany at that time probably represented mostly poma- 

 ceous types. There is every reason to believe that P. expansum as de- 

 scribed by Link represents the species as we know it today. Having 

 described P. expansum, and in some measure differentiated it from P. 

 glaucum in 1809, Link in 1824 abandoned the species and referred all green 

 Penicillia to P. glaucum-. This practice has been followed all too generally 

 to the present day, with the result that the name P. glaucu7n is now prac- 

 tically meaningless and almost any green Penicillium may be found referred 

 to it. 



Members of the Penicillium expansum series are not uncommon in or 

 upon organic materials in contact with the soil. They occasionally occur 

 upon grains and cereal products derived therefrom, including bread. They 

 have been isolated from eggs and chickens in cold storage, and from the 

 waste sulphite liquors of the wood pulp industry. They occasionally occur 

 upon fabrics and other deteriorating military equipment. They are, how- 

 ever, most common and most characteristically isolated from ripe fruits, 

 particularly apples and other pomaceous types, either in storage or as they 

 reach the consumer-market. They typically produce a soft, brown rot 

 that is highly destructive and which may spread rapidly through a storage 

 area in the absence of adequate precautionary measures. Spores of the 

 fungus are carried from the field on the surface of the fruit, and germinate 

 and enter through cuts and abrasions in the cuticle and epidermis. Sizable 

 areas of rot may develop before the mold reappears at the surface in the 

 form of blue-green tufts of massed conidiophores, which often-times may be 

 2 to 3 mm. high and represent well defined coremia (fig. 130 A). 



When tested in the laboratory by piercing and inoculating sound apples, 

 typical strains of Penicillium expansum will produce areas of rot from 3 to 

 4 cm. in diameter, extending inward to the core, within a period of 8 to 10 

 days (fig. 130B and C). Areas of green sporulation develop within two to 

 three weeks at room temperature. 



Penicillium crustosum Thom is also included in the present series, al- 



