PHYSIOLOGY OF TREES. 271 



the stem and branches of a tree contain less sap 

 in the winter than in summer? The question 

 deserves an answer, and may be replied to 

 thus : — The supply of crude sap from the roots 

 is certainly more abundant in the vegetating 

 seasons than in winter ; and this, added to the 

 stock of sap which was arrested by the cold, 

 but now, by the spring warmth, highly liquefied, 

 causes a most copious flow. During summer 

 and autumn, however, the aqueous part of this 

 flow is expended and transpired away, leaving 

 the grosser parts lodged in the vascular mem- 

 bers of the stem and branches, in the interior, 

 and sometimes on the exterior of the buds for 

 their preservation. The woodman is therefore 

 perfectly right in thinking that the sap is more 

 active in the stem and branches in summer, and 

 more fluid and active in the roots than in the 

 stem in winter; but he is wrong in concluding 

 that the activity in the latter case is owing to its 

 having subsided from the top to the bottom of 

 the tree. The fluidity of the sap in the roots 



