EFFECT OF EXTERNAL CONDITIONS 37 



March 17, 1862. 



I am greatly puzzled just now in my mind by a very 

 prevalent difference between animals and vegetables : inas- 

 much as the individual animal is certainly changed materially 

 by external conditions, the latter (I think) never except in 

 such a coarse way as stunting or enlarging — and this is 

 because in animals there is a direct relation between stimu- 

 lated function and consequent change in organs concerned 

 in that function ; e:g. no increase of cold on the spot, or 

 change of individual plant from hot to cold, will induce 

 said individual plant to get more woolly covering, but I 

 suppose that a series of cold seasons would bring about such 

 a change in an individual quadruped, just as rowing will 

 harden hands &c. The cases are not parallel, because the 

 parts of plants that could be so changed are annually lost, 

 and the only conceivable parallel is afforded by bark : would 

 a cycle of cold seasons cause the bark of a tree to thicken 

 more than it otherwise would ? I cannot suppose that the 

 buds of the individual would get thicker, or more scales, 

 or more resinous scales ; or that its successive leaves can 

 become annually more hairy : except indeed we assume the 

 annual death of a large proportion of the buds, and that 

 those alone are preserved that have most ' woolly ' leaves — 

 when no doubt the woolly tendency would be inherited by 

 the successive phytons of that bud, as by successive genera- 

 tions from seeds. 



Be all this as it may, in neither plant nor animal would 

 the induced character be of necessity inherited by the 

 offspring by seed of the individual, to any greater extent 

 than if it had not been changed — at least so far as the animal 

 is concerned ; though with regard to the plant it might be, 

 the seed being that of the phyton, not of the whole tree, or 

 average tree. Thus a wild complication is introduced into 

 the whole subject that perplexes me greatly. 



Berkeley's article on acclimatization is very unclear I 

 think (see last Saturday's Gardeners' Chronicle). 



I cannot conceive what you say, that climate could have 

 effected even such a single character as a hooked seed. You 

 know I have a morbid horror of two laws in nature for 

 obtaining the same end ; hence I incline to attribute the 

 smallest variation to the inherent tendency to vary ; a 



