434 G. p. PLAISANCE AND B. W. HAMMER 



that used for plating) and were then tested for mannitol-pro- 

 ducing power by inoculating into sterile corn juice, sterile stover 

 juice, a sterile corn silo or a sterile stover silo, allowing growth 

 to go on for a period varying from a few days to several weeks, 

 and then examining the material for mannitol. 



Attempts were made to isolate mannitol-producing organisms 

 from a number of samples of silage that had been ensiled several 

 months but only negative results were secured. Yeast^ colonies 

 were commonly present on the plates in considerable numbers 

 and often made up the greater part of the developing flora; 

 many of these were tried out for mannitol-producing power but 

 when the yeasts were in pure culture mannitol was never found. 

 Other types of silage were then studied and the first mannitol- 

 producing organism isolated — M39 — was secured from silage 

 fourteen days old that was made by ensiling green corn from the 

 greenhouse; the silage contained 1.09 per cent mannitol at the 

 time it was plated out. The colony from which M39 was secured 

 was very small and comparatively few of its kind were present; 

 the organism was found capable of producing mannitol in sterile 

 corn juice, in sterile stover juice, in sterile corn silos, and in 

 sterile stover sucrose silos and has consistently given mannitol 

 in a large number of trials. 



Mannitol-producing organisms were readily isolated from a 

 sample of corn juice that was covered with oil (to keep down 

 mold growth) and allowed to ferment spontaneously and that 

 showed, after a short period, considerable quantities of mannitol. 

 A direct microscopic examination showed many yeast cells and 

 still larger numbers of bacteria. On plating out, on corn juice 

 agar, material from both the upper and lower layers of this fer- 

 menting juice, colonies similar to those of M39 were found in 

 large numbers, together with many yeast colonies. When the 

 colonies similar to those of M39 were streaked on agar slopes 

 and then inoculated into either sterile corn juice or a sterile 

 silo, mannitol was found in considerable amounts after the usual 

 holding period. 



* The term yeast is used to indicate organisms reproducing by budding. 



