ECONOMIC IMPORTANCE OF FUNGI 



317 



and in part by the action of an enzyme (galactase) inherent 

 in the milk from which the cheese is made. 



296. Vinegar. Cider vinegar is in every respect a 

 plant product. It is formed from the juice of apples, and 

 ripens or "ages" under the influence of bacteria. These 

 bacteria produce an enzyme which causes "acetic acid 



FIG. 228. Roots of soy bean plants. A, from seeds that were soaked 

 in soy bean bacterial culture over night; B, roots of check plant (not inocu- 

 lated). (After Carman and Didlake. Courtesy of Kentucky Agr. Exp. 

 Station.) 



fermentation." This is the acid to which vinegar owes 

 its sourness. There is not room here to explain the 

 process of vinegar making in detail. 



297. The Secret of Clover. Farmers have known for 

 many years that a given piece of land produces a larger 

 yield if the same crop is not grown continuously, season 



