Mar. 4, 1918 



Corn-Stover Silage 



595 



Table IV. — Groups of bacteria present at different stages of curing 



Age. 



Percentage of total number. 



Acid-non- 

 coagulat- 

 ing group. 



Weeks. 



3/7 



I 



2 



3 



5 



6 



8 



10 



12 



Inert 

 group. 



23 



14 



9 



10 

 O 



o 

 o 



Table IV shows that the rather complex bacterial flora which is present 

 at the beginning of the process gives way to one which is almost entirely 

 acid-producing as the fermentation progresses. The proportion of 

 acid-forming and coagulating organisms to the noncoagulating ones 

 also increases as the curing period advances. A comparison of these 

 figures with those given in Table III indicates that the change in flora 

 is not to be accounted for by an actual increase in the high acid-forming 

 organisms during the latter part of the fermentation period, but rather 

 to the fact that they do not decrease as rapidly because of their greater 

 resistance to the unfavorable hydrogen-ion concentration. 



The division of the acid-forming organisms into coagulating and non- 

 coagulating types, though convenient and significant for the present 

 purpose, probably does not separate them into natural groups. From 

 early in the fermentation the predominating organisms were acid formers, 

 most of which probably belonged to the same general group'. We have 

 found cultures which were apparently identical, as indicated by the 

 cultural and fermentative reactions studied, but which varied in the 

 amount of lactic acid produced in milk from only 0.3 to more than 2.0 

 per cent. All of these probably belonged to the same general group as 

 the aciduric bacteria which have previously been noted as occurring 

 abundantly in silage. In the first two samples examined organisms of 

 the colon-aerogenes group were found and ^Iso a few cultures which 

 were probably Streptococcus lacticus, but tests were not applied which 

 would definitely identify the latter. 



NATURE OF SILAGE FERMENTATION 



Until recently the cell-respiration theory of silage fermentation estab- 

 lished by Babcock and Russell (/, 2) has not been seriously challenged. 

 During the past year, however, several publications ha\e appeared in 

 support of the bacterial explanation of this phenomenon. In view of 

 the recent contributions to the subject, it is not out of place to examine 

 38324"— 18 6 



