THE EFFECTS OF CONDITIONS OF LIFE. 311 



ment. The inference is only that they may be, if not 

 wholly, then in part. 



Among plants, a striking instance of the apparently 

 direct action of conditions of life in the production of 

 variations has been afforded by Meehan.* This ob- 

 server " has compared twenty-nine species of American 

 trees with their nearest European allies, all grown in 

 close proximity and under as nearly as possible the same 

 conditions. In the American species he finds, with the 

 rarest exceptions, that the leaves fall earlier in the sea- 

 son, and assume before they fall a brighter tint; that 

 they are less deeply toothed or serrated; that the buds 

 are smaller; that the trees are more diffuse in growth 

 and have fewer branchlets; and lastly, that the seeds 

 are smaller all in comparison with the corresponding 

 European species." f The trees compared belong to 

 several distinct orders, and are adapted to widely dif- 

 ferent stations, hence Darwin considers that the ob- 

 served differences should be " attributed to the long 

 continued action of a different climate." 



More conclusive evidence of the direct effect of en- 

 vironment has been obtained in the case of Alpine 

 plants. The especially characteristic features of these 

 plants, as compared with similar or allied plants growing 

 at lower levels, are a dwarfing in size and compactness 

 of growth sometimes giving rise to a moss-like appear- 

 ance; a more intense green colour in the leaves, and 

 greater brilliancy and size in the flowers; an increased 

 hairiness of the leaves, and occasionally a certain degree 

 of fleshiness of the tissues. Now by growing lowland 



* Proc. Acad. Nat. Sci. of Philadelphia, January 28, 1862. 

 f Quoted from "Animals and Plants," ii. p. 271. 



