previous year's decayed tubers and haulms whether lying in 

 fields or in manure heaps, and the oospores, which possess 

 greater power of resisting climatic conditions than the non- 

 sexual reproductive tissues such as mycelia, conidia and 

 zoospores, germinating in the hill districts in spring at or 

 immediately before the potato sowing season, the treatment 

 indicated is both preventive and curative. Sulphate of 

 copper solution or corrosive sublimate may be sprinkled on 

 the field with the help of a knapsack vaporiser immediately 

 before the potatoes are sown. .Then the crop should be care- 

 fully watched and if any black patches and white bloom 

 appear at the lower surface of the leaves at any portion of 

 the field, the vaporising should be repeated. One preventive 

 and two curative treatments should be sufficient. But if 

 treatment is not feasible all over a tract affected with potato- 

 blight, it is best to give up potato cultivation for three or four 

 years, that the vitality of the resting-spores may die out before 

 potato cultivation is resumed in that tract. This is how the 

 potato blight which ruined the crops in the Darjeeling hills 

 about ten years ago, had to be faced. There was entire sus- 

 pension of potato cultivation for three years all over these 

 hill?, and since then the disease has not reappeared. 



1.368. In France, the potato-blight was successfully com- 

 bated with the help of the Bouillie bordelaise t ort\\e Bordeaux 

 mixture which consists of a half per cent, solution of sulphate 

 of copper in hot water to which a quantity of milk of lime 

 is added. This was applied with the help of the knapsack 

 spraying machine called Eclair Vaporiser, both before sowing 

 and two or three times after germination of the seed, during 

 the growth of the crop. 



1.369. Rust. This is a disease of cereal plants caused 

 by a minute fungus known as Puccinia graminis. There are 

 different species of Puccinia graminis, the commonest of which 

 attacking wheat, is called Puccinia rubigo-vera. This puc- 

 cinia is different from the puccinia known to attack oats or 



