101 



visions oi properties bestowed upon the tree itself. In the 

 first place, a tliickei and closer ramification of the sides and 

 top is suppHed, and a more abundant spray towards the 

 stormy quarter, thereby furnishing a kind of clothing of 

 leaves, in order to protect from cold both the ascending, and 

 the descending sap-vessels : And secondly, a greater indura- 

 tion of the epidermis, and thickness of the cortical layers 

 of the bark are provided ; which, forming a bad conductor 

 of heat, act as a still more effectual defence to the stem, by 

 preventing the immediate and powerful application of cold, 

 through the sudden subtraction of caloric, from the proper 

 vessels of the inner bark. 



In this economy, nature only follows the analogy which 

 she displays, in modifying the influence of cold upon the 

 animal kingdom. The quadrupeds, which are destined to 

 encounter the severity of an arctic winter, are provided with 

 thick and shaggy coats, to enable them to withstand the 

 intensity of the cold ; and all the richest furs, which man 

 employs to supply his natural, or rather his artificial wants, 

 are always furnished by animals inhabiting the highest lati- 

 tudes, and killed during the severest frosts. What is siill 

 more illustrative of the point under consideration is, that the 

 coats of animals, of which the thin and short hair is familiar 

 to us in the temperate climates, such as the dog, the fox, and 

 the ox, are all remarkable, under the polar regions, for their 

 close, lengthened, and almost impenetrable fibre, as a se- 

 cure barrier of non-conducting matter, to prevent the escape 

 of their vital heat.* 



In like manner, in all the other relations, we see nature 

 especially accommodating the character of each individual 

 plant to the exigencies of its particular situation. In the 

 interior of woods, the wind can exert a far less mechanical 

 effect on individual trees ; and therefore, while they are 



* Note V. 



