420 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



arising from the same causes, such as want of intelligent care, 

 badly located establishments, etc. Nearly all careful and well- 

 instructed managers who use the improved methods of selec- 

 tion succeed in their work. For these reasons, M. Meneville 

 is satisfied that the silk-worm epidemic wdll decrease more and 

 more each year, and that very soon we may hope to see the 

 silk-producing interest in its normal condition ; and even 

 though eggs may not be exported to China and Japan, it will, 

 at least, be unnecessary to import any more from those coun- 

 tries, 6 B.JunedO, 1873, 1612. 



PKIZE FOR AN ESSAY ON THE POTATO DISEASE. 



The Royal Agricultural Society of London has lately offer- 

 ed a prize of 100 sterling for the best essay on the potato 

 disease and the modes of its prevention. The competing 

 essays arc to be sent in before the end of 1873, with the pro- 

 viso that all the information they contain shall be founded 

 on experience and original observation, and not upon com- 

 pilations from books or other writings. 



A summary of what is believed to be known on the subject, 

 prepared by Mr. Caruthers, has been published by the Socie- 

 ty to aid essayists in their labors. In this we are informed 

 that the potato disease has been known for ages in the w^est- 

 ern countries of South America, but that its first ascertained 

 appearance in the United States and Canada w^as in 1843. It 

 re-appeared in these countries in the following year. In the 

 latter half of July, 1845, it first appeared in Belgium, and 

 within two months its presence was recorded in England, 

 Ireland, Scotland, France, Germany, Denmark, and Russia. 

 Since that period it has never been entirely absent from the 

 potato crojis, although less destructive in some seasons than 

 in others. 



The report goes on to state that there is no longer any dis- 

 pute as to the real cause of the disease, namely, a microscop- 

 ic fungus. That this is the cause, and not the effect, is 

 shown by the fact that the disease has been produced in 

 healthy plants by transferring the spores to the leaves or 

 tubers. These spores or seeds are ovoid bodies, not more 

 than -g-o-oth of an inch long. When one of them rests on 

 the under surfiice of the leaf, with sufiicient moisture present, 

 it pushes out a slender tube through its own ruptured coat, 



