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



METHODS USED 



In order to prevent repetition, some of the materials used 

 are here described. The corn juice was secured by pressing 

 green corn, while the stover juice was obtained by soaking corn 

 stover in water for twelve hours and then pressing. The corn 

 silos were made by packing chopped green corn, and the stover 

 silos by packing chopped stover, and adding a calculated amount 

 of water and usually about 5 per cent sucrose, calculated on a 

 dry basis. For most of the silos, the material was packed in 

 quart Mason jars but in a few instances bottles or flasks holding 

 from 1 to 2 liters were used. 



Corn juice agar was made by adding 1.5 per cent agar and 

 1 per cent pepton to the corn juice while the stover juice agar 

 was made by adding 1.5 per cent agar, 1 per cent pepton and 

 5 per cent sucrose to the stover juice; the stover juice agar was 

 commonly cleared with an egg when it was wanted for plating 

 but this was not necessary with the corn juice agar. The corn 

 juice agar was more satisfactory than the stover juice agar 

 because it was lighter in color and apparently gave a more 

 satisfactory growth. 



The method of isolating and determining mannitol in silage 

 was that used in the former work at the Iowa station which has 

 already been referred to. Mannitol was determined in liquid 

 cultures by evaporating 100 cc. aliquot to dryness on a steam 

 box; the residue was then extracted five times with boiling 95 

 per cent alcohol (about 15 cc. of alcohol in each portion) and 

 the combined extracts filtered as soon as cold. After standing 

 over night the mannitol had crystallized; the crystals were 

 sucked dry, recrystallized from water and alcohol, dried and then 

 weighed. 



RESULTS SECURED 



The role of microorganisms in mannitol production 



Although in the previous work at the Iowa station the pro- 

 duction of mannitol was secured by inoculating sterilized stover 

 (plus sucrose and water) with a decoction of a leaf of corn silage 



