SAP IN 'TREES. 205 



part of the wound than at the under, without finding a 

 cause for it in the particular state of the bark, nor have 

 we seen any thing that we could consider as a down- 

 ward motion of the sap in summer, or of an upward 

 one in the spring. 



Upon a subject where so many eminent men have 

 given their opinions, and where these are so much at 

 variance with each other (except in those instances in 

 which it is clearly doctor and disciple) we would not 

 wish to speak decidedly. There is no class of subjects 

 upon which one can trust so little to experiment as 

 growing vegetables ; they are so docile in the hand of 

 man, that one never can find out how much of the re- 

 sult depends upon the natural functions of the plant, 

 and how much upon what is done to it by the experi- 

 menter. Even in the case of an animal, we cannot 

 try it much without teaching it a little ; and the plant 

 is, from its being rooted to one place, much more liable 

 to be acted upon by the treatment that we give it. We 

 have had repeated cause to notice the fancies that 

 have been introduced into the natural history of ani- 

 mals, by reasoning upon the analogy of man, and 

 when we find the great discrepancy that there is between 

 the theory and the facts, we are very much inclined to 

 suspect that there have been a great many fancies in- 

 troduced into the natural history of vegetables, in con- 

 sequence of animal analogies. These fancies have pro- 

 duced false explanations, and, therefore, prevented the 

 true ones from being sought for. 



We have no proof whatever that there is any circu- 

 lation in a plant, either upward in the spring when 



