186 DEATH OF THE THEE FOUNDED ON 



preservative against the exhausting influences of its flowers, 

 or reproductive organs, yet, nevertheless, it dies sooner or 

 later ; and this question arises for consideration : Is the 

 death of the tree brought about in accordance with a regu- 

 lar law to which its organism is subjected ? or does it pos- 

 sess a natural tendency to an unlimited duration of life, 

 which is only brought to an end, accidentally, through 

 storms and other hurtful .outward influences ? The former 

 appears to me to be the correct view, and I am sustained 

 in this opinion by linger* and Mohl,f both eminent phy- 

 siologists. 



We have seen that every part of the tree is a representa- 

 tive of a certain stage of development through which the 

 tree has passed, whether it be leaf, shoot, or branch. But 

 each of these parts passes through certain regular stages of 

 infancy, maturity, decay, and death. 



Now the growth of all the leaf-forms temporarily put 

 forth by the tree, as well as the shoots and branches which 

 remain permanently connected with its structure, is accele- 

 rated during the earlier part of their life, and retarded as 

 they arrive at maturity and towards its close. Thus the 

 growths made yearly are accelerated during the early part 

 of the vegetative season, when the conditions are the most 

 favorable, and gradually retarded as the season advances ; 

 till, finally, the growths cease altogether, and the tree con- 

 tinues in a state of passive vitality through the winter 

 months, being in precisely the same condition as a seed 

 before it germinates. With the return of spring and warm 

 weather, the vitality of the seed and tree again becomes 

 active; the former germinates, and the latter puts forth 

 new leaves and shoots, and is again covered with its usual 

 exuberance of foliage. This we have called, in Chapter 

 VI, the " annual wave." 



But there is also a "grand life wave." For these yearly 

 growths themselves,. I mean those made by the main stem 



* Grundz. d. Anat. u. Phy. S. 131. 

 f Vegetabilische Zelle, S. 65. 



