DISEASES AND INSECTS. 377 



their deportment under reasonably favorable 

 conditions of growth. What we should all of 

 us do, therefore, is to study diligently the laws 

 and conditions which are concerned in the pre- 

 servation of health in plants, oiyin other words, 

 the conditions that are necessary to normal de- 

 velopment and hardy growth. These we have 

 already so fully stated and so earnestly insisted 

 upon, that it is unnecessary to dwell upon them 

 here. 



Mildew. This is a wide-spread and destruc- 

 tive disease, and difficult to manage when estab- 

 lished. It is also known by the botanical names 

 Erysiphe and Oidium. In portions of Europe 

 the Oidium Tuckeri has at times been partic- 

 ularly fatal. With us it has been much less 

 injurious. Mildew is a parasite in the form of 

 a fungus, and attacks the leaves, fruit, and 

 wood. It first makes its appearance on the 

 under side of the leaf, like a fine mould. The 

 mycelium penetrates the tissue of the leaf, and 

 destroys it, when the leaf becomes discolored in 

 spots, showing where the fungus is at work. 

 In this place we can not do more than .state 

 briefly some of the causes and conditions which 

 produce the disease, with the remedies that 

 have proved most effectual in subduing it. 



