ON THE TOrNfl BARK, 27 



but of those general and peculiar laws of growth which 

 govern the entire tree itself. All the apparent confusion 

 and irregularity among the branches and branchlets of a 

 tree is the result of the operation of fixed and immutable 

 laws of growth, to which the whole tree is subjected in com- 

 mon with each of its parts. The entire tree is not different 

 from one of its branches in the principles of its construc- 

 tion. In fact, if one of the branches were severed from 

 the stem and planted, it would not only represent one of 

 the phases of growth of the tree, at an earlier stage of its 

 life, but under favorable circumstances would actually 

 grow into a separate and independent tree. 



In this, as in the figures of leaves, we have avoided an ex- 

 travagance of illustration, in order that our book may not be 

 rendered too expensive. Besides, it is unnecessary. Trees 

 are all constructed on the same general plan. Hence, we 

 have taken our material, not from deep resources, but from 

 common objects. It is proper here to remark, that the 

 reader will understand more clearly the positions assumed, 

 if he procure a number of branches of different trees, such 

 as the beech, the hickory, the horse-chestnut, when defo- 

 liated or in winter, and attentively study the marks on the 

 exterior of the bark and the mode of ramification. If the 

 branches are gathered when the trees are in leaf, the foli- 

 age must be removed. 



The reader is already prepared to admit, without further 

 proof, that the growth of the tree is very fluctuating, and. 

 is greatly influenced by changes in the weather. In this 

 respect, the organism of a tree is quite as sensitive as the 

 mercurial column in the tube of a barometer. It is well- 

 known that the age of a tree may be ascertained by count- 

 ing the rings visible on the cross section of its stem, and 

 that the impress of centuries of seasons has been faithfully 

 recorded in its woody layers. The seasons also leave their 

 mark on the outside as well as the inside of the tree. When 

 the young shoot, in early spring, unfolds itself from the bud, 

 and the brown scales which enveloped the young leaves 

 fall off, they leave ring-formed or annular scars at the hot- 



