94 CULTURAL STUDIES OF SPECIES OF PENICILLIUM. 



SUMMARY OF DATA FROM COMPARATIVE CULTURE. 



1. Species closely related in morphology and general appearance 

 give closely similar reactions in culture under most conditions, but 

 commonly show a few well-marked differences in special media or 

 under special conditions. 



• 2. Certain species will grow in media of widely differing composi- 

 tion; others require particular media for normal development. 



3. Cane sugar in low concentrations is readily assimilated by 

 every species studied. 



4. Butterfat was attacked by nearly every species. 



5. Lactose, galactose, levulose, and glycerin are assimilated by 

 some species and not by others. 



6. Potato starch produced normal growth in most species. 



7. Very few species grew at 37° C; i. e., very few species could 

 be parasitic to w T arm-blooded animals. Few species were killed at 

 37° C, and species not killed grew normally when the medium was 

 cooled to 20° C. 



8. Incubation at low temperatures shows that growth in some 

 species will begin at temperatures very close to the freezing point, 

 but that only a few species will actually develop in cold-storage 

 temperatures. 



9. None of the species was found to grow in an atmosphere of 

 carbon dioxid, but no species was killed by such atmosphere. 



10. In most species failing to grow in a particular medium a 

 change of concentration or the addition of a missing element will 

 permit normal growth unless killed by osmotic pressure or definitely 

 toxic agents. 



KEYS TO CULTURAL IDENTIFICATION OF SPECIES. 



Media: Prepare the following media — 



1. 15 per cent gelatin in distilled water. 



2. 15 per cent gelatin in distilled water plus 3 per cent cane sugar. 



3. Either bean or potato decoction plus 1.5 per cent agar. 



4. Bean or potato agar plus 3 per cent cane sugar. 



Litmus solution may be added if desired when cultures are made. 



Prepare Petri dishes with 10 c. c. of each of the media used and 

 allow them to cool. Inoculate two or more Petri dishes of each 

 medium with spores of the species under examination. Incubate 

 at 20° C. (the temperature of the working laboratory is usually 



a In most of these studies the "gold-label" gelatin imported by Bausch & Lomb 

 from Germany has been used. Culture of a species in a solution of gelatin in water 

 has two uses in this paper — the detection of the production of enzyms capable of 

 liquefying this medium, and the estimation of the ability of the species to grow in a 

 medium free from carbohydrates. Neither of these tests seems to be vitiated by 

 media made up at different times from materials of different origin. Such differences 

 as are induced by the differences in the gelatin are quantitative, not qualitative. 



