103 



with or arising from causes affecting their vital power 

 — for these remarks exhibit facts and reasons estab- 

 lishing the existence of such power in plants — we 

 will proceed to consider in detail the most prevalent 

 diseases of the plant now under consideration. 



Ulcer or Canker. — This class of disease, to 

 which in some form every vegetable is hable, affords 

 a strong demonstration of the vitality — the sensitive 

 energy of life — existing in plants. In dead organic 

 matter decay is total, and pervades the whole mass 

 simultaneously, but when decay or decomposition 

 attacks a living plant, or a living animal, it is local 

 — and the decomposition is restrained within bounds 

 by the wondrous antiseptic power of the vitality in 

 the other parts of the plant. The pine apple affords 

 an illustration of this phenomenon. 



Its suckers taken off from their parents^ before 

 their lower ends are brown — that is, before the 

 woody fibre is sufficiently perfected — are very liable 

 to canker or ulceration in that portion placed within 

 the ground. The same disease often attacks more 

 perfectly matured suckers if these are supplied at 

 first too liberally with water. It is a curious phe- 

 nomenon, that the upper portion of the leaves of 

 suckers, the basis of which are perfectly ulcerated, 

 continue as green, or even greener than those of 

 plants undiseased. The obvious prevention of this 



