AN INNER LAW OF ITS ORGANISM. 187 



loses the power of unfolding itself, and finally dies. "With 

 the death of the terminal bud, and the cessation of the 

 formation of any more leaves, the further growth of the 

 branch is necessarily completely arrested. 



The same remission of growth shows itself in the de- 

 velopment of the branches, whose growth is gradually 

 retarded from one generation to another. The power of 

 any branch to give forth branchlets is not indefinite, but 

 has its appointed limits. New shoots are annually put 

 forth by the terminal and lateral buds of the branches, 

 until the vegetative powers of the branch are completely 

 exhausted. That, in each succeeding generation of shoots, 

 these powers are more and more enfeebled, is evident if we 

 cast only a momentary glance at the branch and its branch- 

 lets. We see that the branchlets become gradually smaller 

 and finer in proportion as their connection with the parent 

 branch is more remote, until finally the leaves which they 

 put forth are too enfeebled in their vitality to produce 

 buds, their axils remaining unfruitful, and all further ra- 

 mification is thus necessarily arrested. 



It is the nature of all living organisms, whether animal 

 or vegetable, to be running through one perpetually recur- 

 ring cycle of the same life-changes, of infancy, maturity, 

 decay, and dissolution. The compound plant called a tree, 

 is no exception to this universal law of Nature. We have 

 seen that, in the earlier portions of its life, it is represented 

 by each of its parts. These parts do not all die at the 

 same time, and their individuality is strikingly indicated 

 by their different periods of life. Thus, the cells of the 

 wood and bark, together with the different varieties of leaf- 

 forms, called by botanists bud-scales, stipules, bracts, se- 

 pals, petals, stamens, and pistils, have all a life peculiar to 

 themselves. The bud-scales have arrived at the close of 

 life when the green leaves of the stem are in their infancy, 

 and in spring make their appearance, and throw off their 

 winter envelopes ; and the petals and stamens die when the 

 pistils begin to mature. Even the vitality of the walls of 

 the ovary, or seed-vessel itself, is exhausted in the forma- 



