86 CULTURAL STUDIES OF SPECIES OF PENICILLIUM. 



region. Apparently glycerin presents a form of carbon much less 

 available for assimilation by species of this genus than the sugars. 



Butterfat (Table 4.). — To test the ability of these fungi to assimilate 

 fat, butter was melted, strained, filtered through filter paper, and 

 added to Dox's fluid. Although not chemically pure, perhaps, it 

 is believed that the amounts of other nutrients would be too small 

 to affect results. Only one form (P. digitatum) failed to grow. 

 P. luteum gave only slight growth. The majority of forms, although 

 growing slowly, produced typical or fairly characteristic colonies. 

 The masses of fat were visibly much changed, becoming incrusted 

 with a white substance in most cultures. In a few cultures the 

 action of fungus caused the separation of the various fats, so that 

 drops of yellow oil separated out from the remaining nonliquid 

 matter. 



Potato starch. — In one series twenty-seven forms were cultivated 

 in Dox's fluid, containing 3 per cent of potato starch. All of the 

 common species of the genus were found to grow normally upon a 

 medium containing starch as the source of carbon. The characters 

 in this medium were approximately the same as in the stock agar 

 or gelatin cultures. Two species (P. decumbens and P. digitatum). 

 which failed to grow well have since been shown to depend upon 

 the presence of cane sugar for vigorous growth and green color to 

 their spores. Similarly the same species grown upon plugs of potato 

 failed to produce strong colonies of pronounced green color. 



Malic and succinic acids. — Series of cultures were made with 

 1 per cent malic acid and with 1 per cent succinic acid as sources 

 of carbon. All species germinated, but no species reached fully 

 typical development in either series. Some few species produced 

 slowly colonies of half or more of the normal size with conidial 

 masses of typical color. Many of the species grew sufficiently to 

 produce a few conidial fructifications recognizable with the hand 

 lens. These two series emphasize the observation already made 

 that species inoculated into a medium ill adapted to their nourish- 

 ment will nevertheless grow and produce small amounts of fruit 

 under widely different conditions even where normal growth is 

 impossible. 



CULTURES IN RAULIN's FLUID AND COHN's SOLUTION. 



The comparative data for. cultures in Raulin's fluid and in Cohn's 

 solution are shown in Tables 3 and 5. Raulin's fluid, as given by 

 Smith, is a highly acid medium and has been found very well adapted 

 for the growth of certain species. The solution is, however, too 

 complex to make analysis of cultural results upon it readily possible. 

 It contains carbon in three different forms — tartaric acid, potassium 

 carbonate, and magnesium carbonate — and nitrogen in two forms 



