XVII. 



ELONGATION" OF TEEE TRUNKS, ETC. 



TO many, it is a mystery how the tops of trees, 

 which, when young, are within a few feet of the 

 ground, become elevated, often fifty feet or more, 

 when the tree has become of large size. Some 

 have supposed that the trunk below the branches 

 gradually lengthens in some way, carrying the top 

 up with it. Those who will observe and reflect 

 upon the subject, however, wUl readily discover 

 that the top which appears upon a large tree is not 

 the one which it had when it was small, but that, 

 with the exception of the main stem, which has 

 become the trunk, the top of the small tree has 

 wholly disappeared, its limbs having died naturally 

 one by one, or having been removed artificially, as 

 other limbs were developed above. In the forest, 

 where there is little light, and the trees are crowded 

 by others, these lower limbs disappear japidly, and 

 the tree soon becomes tall, as it reaches upward 

 after more light. In the open ground, on the other 

 hand, where there is no obstruction, the lower 

 limbs continue to grow, and the top remains low. 

 In either case there is no elongation of any part of 



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