EVERGREENS. 147 



belt, and rendered the trees stunted there, the trees 

 arrested their progress, and rendered much service to the 

 cultivated ground. 



This subject is universally deserving of a great deal 

 more attention than it yet has met with, both as a 

 part of natural history and of rural economy ; and, as 

 indeed should be the case with every part of nature, it 

 should be watched for a long time in the field before 

 there is much speculation about it in the closet. 



Evergreens are altogether a very curious part of the 

 economy of nature, and they somewhat perplex those 

 physiologists that make plants the mere creatures of a 

 given temperature. The surface from which the leaf 

 of a laurel, or the spine of a fir, falls in May or June, 

 when the young shoots and tender leaves have come 

 into vigour and the plant is in the state of greatest 

 activity, is no more a wound than that from which the 

 leaf of the mulberry is separated by the very first frost 

 of the season, or the leaf of the apple and the peach 

 is dropped at a more advanced stage of the cold. The 

 leaf of the deciduous tree falls when the annual action 

 of the tree ceases, and that of the evergreen when the 

 plant is in the full height of vegetation ; and each of 

 them equally cicatrizes the wound by a coating of na- 

 tural varnish. From the differences in the circum- 

 stances under which those two analogous operations 

 are performed, we must infer that there is a difference 

 in the mode of operation ; and that, though a certain 

 state of the air and the matter with which the air is 

 loaded, be necessary to bring about the fall of the leaf, 

 whether in the cold season or in the warm, it is always 

 accompanied by some particular action in the plant, 



