CH. VIII.] THE DISEASES OF PL.A.NTS. 295 



grafts or buds from trees not affected by the disease, 

 because, apparently, it is hereditary ; and, although 

 after-culture may eradicate the malady, it is always 

 far better to avoid the infection than to have to 

 employ a specific. 



Having noticed the gangrene as it appears in 

 various forms upon our trees, we may now turn to a 

 few of the many instances where it occurs to our 

 fruits and flowers, for it is not too much to say that 

 scarcely a cultivated plant is within our enclosures 

 that is not liable to its inroads. It assumes dif- 

 ferent aspects, and varies as to the organs it assails, 

 yet still in some mode and in some of their parts all 

 occasionally suffer, for it is the most common form of 

 vegetable disease. 



The canker in the auricula is of this nature, being 

 a rapidly spreading ulcer, which, destroying the whole 

 texture of the plant where it occurs, prevents the rise 

 of the sap. Some gardeners believe it to be infectious, 

 and therefore destroy the specimen in which it 

 occurs, unless it be very valuable; but this I believe 

 to be an erroneous opinion, the reason of its appear- 

 ing to be infectious or epidemic, being that it occurs to 

 many when they are subjected to the same injurious 

 treatment which gives birth to the disease. 



It appears to be caused by the application of too 

 much water, especially if combined with superabund- 

 ant nourishment. Therefore, although cutting out 



