290 BOAED OF AGRICULTURE. 



These organized ferments, which belong to the class of 

 fungi, may be divided into two groups, the Saccharomycetes 

 or budding fungi, — the active agents of alcoholic fermenta- 

 tion, of which yeast may be taken as the type ; and the 

 Schizomycetes y or fission fungi, which include the lactic, 

 butyric, and similar ferments, and the ferments of putrefac- 

 tion ; most of them are of the forms known as bacteria, 

 and they multiply rapidly by subdivision. All the members 

 of both groups probably propagate by means of spores, but 

 this method of reproduction has not been observed in many 

 species belonging to the last mentioned group. 



The living organisms of fermentation found in samples of 

 fresh ensilage, all belong to the group of Schizomycetes 

 (bacteria). No members of the group of Saccharomycetes 

 (yeast or alcoholic fungi) have been observed in samples 

 from the interior of the silo that had not been exposed to the 

 air. 



After the silo is opened and a large surface is exposed to 

 the air, the " yeast fungi " and even the " moulds " may be 

 found, but they are evidently the result of germs derived 

 from the air after the silo is opened. 



We do not include the " mould fungi " in the class of fer- 

 ments proper, as Pasteur has shown that they act as ferments 

 under exceptional conditions only, and even then they do 

 not produce active fermentation. 



The ferments of the first mentioned group have been 

 studied more thoroughly than the others, from their import- 

 ance in the manufacture of beer, wine, etc., but many of the 

 facts developed in their investigation are undoubtedly appli- 

 cable to the ferments of the other groups. 



From experiments with fruits in an atmosphere of carbonic 

 acid, Pasteur has apparently shown that any vegetable cells 

 which are capable of extracting their needed supply of oxy- 

 gen from organic combinations may, by this manifestation of 

 their vital activity, act as ferments ; and the true ferments are 

 distinguished from these, not by a difference in their specifi- 

 cation, but from the fact that they are capable of carrying on 

 the functions of nutrition and assimilation with much greater 

 activity without a supply of oxygen in the air. 



Pasteur has likewise proved that the alcoholic ferments 



