CH. IX.] DEATH AND DECOMPOSITION. 327 



posed, inevitably bring upon them death ; and it 

 would be mere waste of time to argue against those 

 physiologists who maintain that, in favourable circum- 

 stances, the life of plants may be prolonged in- 

 definitely. Those vrho choose to surmise that some 

 plants would endure throughout all time, if unfail- 

 ingly preserved from all things offensive, and sup- 

 plied without failure with all things agreeable, 

 amuse themselves with imaoining what would occur 

 under circumstances of impossible attainment. 



A plant must be subjected to unfavourable con- 

 tingencies, and the greater the amount and frequency 

 of their occurrence, the more speedily do they bring 

 its life to a close — for the more do they aid chemical 

 affinities in breaking down that resistance of 

 their efforts, wliich is the chief characteristic of 

 vitality. 



So long as a plant lives, it triumphs over those 

 affinities. Its roots overcome the affinity of the 

 soil and take from it its moisture ; its leaves over- 

 come the affinity of the atmosphere, and deprive it 

 of the wateiy vapour it has in solution ; the inter- 

 nal vessels overcome numerous affinities, and, by the 

 decomposition of carbonic acid and water, perform 

 within their simple tubes that which can only be 

 effected by the chemists most powerful agents. 

 These triumphs over chemical affinities — and that 

 most characteristic of triumphs, its avoidance of pu- 



