34 MICEOBES, FERMENTS, AND MOULDS. 



forms floury patches which send forth a peculiar 

 musty smell. 



The oidium may remain latent on the vine-stock 

 throughout the winter. In the spring it reappears 

 in yellowish patches on the earliest leaves, on which 

 it is rapidly propagated ; the plant languishes, and 

 the leaves become pale and, as it were, anaemic. 



Very dry weather is unfavourable to oidium, and 

 so also are heavy rains, which wash the fruit and 

 leaves, and carry away the spores on to the soil. 



The remedy consists in the application of sulphur 

 to the infected vines. Flowers of sulphur is used, 

 which acts upon the fungus by gradually setting free 

 sulphurous acid. Under this influence the microscope 

 shows that the superficial mycelium and the fragile 

 spores dry up as if they were burnt (Ed. Andr^). 

 Three successive applications are necessary, and these 

 are made with the help of a special instrument in 

 the form of a pair of bellows, to which a rose is 

 affixed, in order to disseminate the flowers of sulphur. 

 The first application is made in spring, when the 

 shoots are from eight to ten centimetres long; the 

 second directly after the vine has blossomed; and 

 the third when the grapes begin to ripen. The opera- 

 tion in spring is the most important, and should be 

 performed with the utmost care, so as to afl"ect all 

 the hybernating spores from which the succeeding 

 generations would issue. Not only the upper and 

 lower sides of the leaves must be dusted, but also 



