SECT. III. NATURAL DECAY. 5ll 



But the peculiar vitality which the leaf is here 

 supposed to possess seems to me to be altogether a 

 groundless assumption, and an unphilosophical 

 multiplication of causes without any apparent ne- 

 cessity. Is it not rather the individual vitality of 

 the plant extended to a perishable organ, and again 

 withdrawn when that organ has discharged its des- 

 tined functions, or become by disease or decay 

 unfit for the purposes of vegetation ? This, I pre- 

 sume, is a better founded supposition than the fore- 

 going ; though the reference to the phenomenon of 

 the throwing off of the dead part from the sound 

 part in the animal subject is sufficiently well 

 adapted to the purposes of illustration; and the 

 analogy sufficiently striking, at least under soms 

 of its aspects, to warrant its introduction. For 

 which, or for similar reasons, our learned president 

 Sir J. E. Smith gives his sanction to the opinion of 

 Vorlick, which he had himself indeed been pre- 

 viously led to adopt, though he was anticipated in 

 the publication. The notion was first suggested to 

 him by some remarks of Mr. Fairbairn, of Chelsea, 

 who had observed that in the transplanting of trees, 

 if the injury extends suddenly beyond the leaf, 

 then the leaf remains firmly attached to the twig 

 even though dead ; but when the leaves alone are 

 affected, and the vital energy acting with full force 

 in the branch, the leaves are thrown off or fall upon 

 the slightest touch. Hence Sir J. E. Smith con- 

 cludes that leaves are thrown off by a process si- 



