90 CULTURAL STUDIES OF SPECIES OF PENICILLIUM. 



P. spinulosum , P. expansum, P. hrevicaule. and such floccose forms as 

 P. camemberti and P. biforme; the species of restricted habit with 

 narrow growing border are represented by P. citrinum and P. atra- 

 mentosum and their allies. The designation "spreading," "restricted," 

 "with broad margin," or "with narrow margin" is descriptive for 

 colonies of such species. 



ODORS. 



Although many persons seem to detect the presence of mold by its 

 odor, very many of the species give but little definite odor. A few 

 forms, some of them (e. g., P. biforme) always, others upon special 

 media, produce difinite odors by which they, can be recognized or 

 placed in particular groups. Grown upon gelatin media, P. brevi- 

 caule produces a strong ammoniacal odor. A piece of moistened lit- 

 mus paper held over such a colony will promptly give the alkaline re- 

 action. This organism is recorded as emitting arsin from cultures con- 

 taining arsenic in any form and it is said to be a very delicate test for 

 the presence of that element a (Gosio) . The two forms here described 

 as varieties of P. brevicaule give exactly the same odor. In nearly 

 every medium used P. expansum (the apple rot) gives a strong odor, 

 which suggests decaying fruit to some. Once well distinguished, the 

 presence of this organism can be detected even as a contamination 

 wherever it occurs, by the odor alone. Another given here as P. 

 atramentosum produces a very characteristic odor while digesting milk, 

 defined by one as the odor of rancid walnuts, to another it suggested 

 mice. A series of forms when grown upon cane sugar produce a very 

 characteristic odor — an ester, according to the chemists to whom it 

 was submitted — recognizable to the sense of smell, but not definable. 

 The olive-colored orange rot (P. cligitatum) gives this most strongly, but 

 it is also given by P. italicum, P. decumbens, and No. 13. The odor 

 of P. claviforme is found under nearly all cultural conditions, and 

 would readily identify it were its big coremia not already very distinc- 

 tive. The common and undefinable green group contains a series of 

 races or forms, many of which give what is popularly called the smell 

 of mold. In others of this group this odor is scarcely distinguishable. 



ANAEROBIC CULTURES (WITH CARBON DIOXDd). 



The possibility of some species developing under anaerobic con- 

 ditions was tested as follows: Vials were prepared with Dox's fluid 

 having 5 per cent cane sugar as a source of carbon. This had already 

 been shown to be an excellent medium for the growth of nearly all the 

 species used. These vials, containing all the species herein described, 

 were packed in a crate or test-tube basket and put into a Novy jar. 

 The jar was then given in charge of Mr. Dox. The air was exhausted 



o Gosio. Azione di alcune muffe sui composti fissi d'arsenico. Rivista d'Igiene 

 e Sanita Pubblica, Rome, 1892. See page 201. 



