222 CULTURE OF THE GRAPE. 



Indeed, a somewhat moist state of the air is necessary to 

 their continued life. Hence we find that those climates 

 which are subject to rain and fogs are also most subject 

 to mildew. On the other hand, the dry climate of Cali- 

 fornia, for example, is almost a complete safeguard. It is 

 also true, that this excess of moisture, with heavy dews, 

 and sudden changes from heat to cold, tend to make the 

 grape-foliage feeble or unhealthy, possibly rupturing the 

 pores of the leaves, and destroying the cuticle, which is 

 a guard against the lodgement of floating seeds of fungi. 

 In muggy weather, the foliage is soft and succulent, which 

 is also an assistance in the vegetation of fungus-seeds. 



' O 



It is well known with what anxiety the English farmers 

 watch their wheat-crop during its rapid growth, and time 

 of ripening, lest the mildew, or rust as it is called 

 (Puccinia graminis), should have the favoring influences 

 of their dull weather. M. Duhamel states -tliat mildew 

 is caused by such an atmosphere. Though this may not 

 be strictly true, it is universally observed that such 

 weather greatly favors its development. AVe are to con- 

 sider mildew as a living plant, dependent, like all other 

 vegetable life, upon its conditions of growth. Possibly 

 we may be able to prevent its seed from taking root, or 

 we may produce such a state of the atmosphere that it 



