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with spieading Ijiaiiclieis, in conseciueiice of llie free access 

 of light, are formed as plainly for the nourishment, as well 

 as the balancing of so large a trunk, and also for furnishing 

 a cover, to shield it from the elements. Thirdly, their supe- 

 rior thickness and induration of bark is, in like manner, 

 bestowed for the protection of the sap vessels, that lie imme- 

 diately under it, and which, without such defence from cold, 

 could not perform theii functions. Fourthly, their greater 

 number and variety of roots are for the double purpose of 

 nourishment and strength ; nourishment to support a mass 

 of such magnitude, and strength to contend with the fury 

 of the blast. Such are the obvious purposes, for which these 

 unvarying characteristics of trees in open exposures are con- 

 ferred upon them. Nor are they conferred equally and in- 

 discriminately on all trees so situated. They seem, by the 

 economy of nature, to be peculiar adaptations to the cir- 

 cumstances and wants of each individual, uniformly be- 

 stowed in the ratio of exposure, greater where that is more 

 conspicuous, and uniformly decreasing, as it becomes less. 



On the other hand, in the interior of woods, a universal 

 tendency, for the reasons aheady stated, is observable in 

 trees, to rise to the light, to attain greater altitude, to form 

 far smaller heads, and taller, slenderer, and more elegant 

 stems. Here is found a milder and more genial climate ; in 

 which, by means of the calm generated by shelter, vegeta- 

 tion is not checked by cold, and, at the same time, is undis- 

 turbed by the external impediment of wind. Here nature 

 has no need, as in the case of exposures, to generate pro- 

 visions necessary to mitigate the effect of evaporation, as 

 has been above observed, or to endue each individual tree 

 with distinct and appropriate means of defence against the 

 elements. In this situation, the branches, and, in hke manner, 

 the roots are much less extensive and numerous, than in 

 the former instance, and the bark of a thinner and finer 

 quaUty ; all plainly indicating, that the trees so situated do 



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