284 STUDIES IN THE FIELD AND FOREST. 



sustain the whole plant. This might have been suffi 

 cient for that purpose, during a moist summer ; but on 

 account of the drought of the preceding July, it failed 

 to supply the tree with sustenance, and a premature old 

 age of the leaf and its accompanying tints were the 

 consequence. A severe frost at that early date would 

 have produced no such effect. An early frost always 

 injures these tints by searing and imbrowning the 

 leaves which are exposed to it. This effect was noticed 

 in the autumn of 1853 when the leaves that ripened 

 later than usual, on account of long-continued rains in 

 the latter part of summer, were overtaken by two very 

 severe frosts, before they had begun to be tinted. In 

 October, the effects of these frosts were apparent in a 

 brownish tinge on the outer surface of the trees, greatly 

 impairing the lustre of their tints, which were not so 

 brilliant as usual. 



The cause of the superior beauty of our autumnal 

 hues, compared with those of Europe, is undoubtedly 

 the greater intensity of the sun's rays and the greater 

 proportion of clear and dry weather in America, caus 

 ing. the leaves to arrive sooner to maturity and old age. 

 As these influences do not act in the same way upon 

 European trees when introduced into this country, it 

 would be important to note whether American trees 

 preserve their peculiar habit when transplanted to 

 European soils. There is reason to believe that, while 

 these tints are attributable to the influence of our hot 

 summers and clear skies, the habit was acquired with 

 the. origin of the species countless ages back, like the 

 black skin of the negro, and that it is now beyond any 

 such climatal influence. Though it might have owed 

 its origin to this peculiarity of our climate, the habit is 

 now one of the characteristics of the species. In all 



