28 Director's Report of the 



but worse. The treatment actually reduced the yield by 5,285 pounds 

 on one-half acre, which is at the rate of 5^ tons per acre. 



The treatment fails for four reasons : 



(i) The removal of so many leaves reduces the vitality of the 

 plants; (2) infection occurs through the roots as well as by way of 

 the leaves ; (3) infection may occur at the base of the leaf close to the 

 stem and get into the stem unobserved ; (4) the germs of the disease 

 are so widely distributed that it is useless to try to stamp out the dis- 

 ease by the removal of diseased material. 



No successful method of combating the disease is known. Further 

 investigations on the subject are in progress. 



DEPARTMENT OF CHEMISTRY. 



In addition to the work done in the different lines of inspection, 

 the Chemical Department has been carrying on lines of work as 

 follows : 



The relation of acids in the process of cheese-manufacture to the 

 ripening of cheese. — The study of the relation of paracasein monolac- 

 tate, which was first discovered and identified in this laboratory, to 

 the ripening of cheese, has been continued ; and it has been shown 

 that this compound is of great importance in cheese-making and 

 cheese-ripening, forming the essential compound with which the 

 cheese-ripening process begins. The influence of such factors as 

 time, temperature, moisture, salt and rennet, upon the disappearance 

 of paracasein monolactate in cheese has been carefully studied from 

 a chemical standpoint. 



The sources of carbon dioxide in cheese-ripening. — The results of 

 this chemical work suggest that in normal cheese certain changes 

 occur that can be attributed only to living organisms, which remain 

 yet to be discovered by biologists. 



Rennet-enzyme as a factor in cheese-ripening. — This work, largely 

 chemical, has been carried on in connection with the Bacteriological 



