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DISEASES OF VEGETABLES. 



THAT plants are subject to disease is generally 

 admitted, though it is often difficult to distinguish 

 constitutional distempers from the attack of insects 

 or of parasitical plants. The canker, mildew, uredo, 

 smut, ergot, are all prevalent ; and all other disorders, 

 whatever may be their cause or origin, are compre- 

 hended under the common name Blight. 



Canker appears to be really a constitutional dis- 

 ease. It is a dismemberment and corruption of the 

 organisation, occasioned, it is supposed, by unwhole- 

 some aliment, taken up by the root from ferruginous 

 soils, and which, when lodged in the tender vessels 

 of the young shoots, undergoes some chemical change 

 destructive of the vital envelope and all the other 

 members of the plant. 



It first shows itself in small blisters on the epi- 

 dermis of the young shoots, or round the buds, and 

 at the base of the spurs on the older branches. The 

 taint quickly spreads, corroding every organ in its 

 course. The parts affected become suberous, fractured 

 and monstrous, and are chosen as a nidus by several 

 species of insects, whose larvae feeding on the lips of 



