116 TRUNKS. 



zophora, which grows within the tropics of A9ia and 

 America. It sends forth its numberless branches which 

 descend perpendicularly to the ground, where they 

 take root. From these, other branches arise and pur- 

 sue the same course, as if to extend the dominion of 

 the tree from which they all originate, and at last it 

 covers the country for a mile around, with a forest of 

 numberless branches, having the appearance of a close 

 clipped bower.* 



Those who have observed the progress of the vege- 

 table growth, and seen trees of various sizes produ- 

 ced by the annual deposition of a thin layer of wood ; will 

 be prepared to find a correspondence between the magni- 

 tude and age of the stems they examine. And unless the 

 growth has been particularly rapid, this may be consider- 

 ed as a correct criterion, for the Oaks and the Elms are 

 among the oldest of our forest trees, and the Adansonia 

 is probably not merely the largest, but the oldest 

 vegetable in existence. Indeed, the only limit to 

 the growth of woody stems, is found in their per- 

 ishable nature, which prevents them from retaining, 

 beyond a limited period, strength sufficient to support 

 their own weight. The centre or heart wood being 

 dead, will in the course of a few centuries at least, be- 

 gin to decay, but at the same time, new layers of albur- 

 num are deposited as before. The progress of decay 

 is more rapid than that of renovation, and at last, the 

 hollow trunk being unable to support its own branches, 

 is precipitated to the ground by their growing weight, 

 or overturued by the winds, which it ha* buffeted prob- 

 ably for ages. The durability of the perfect wood, and 

 the strength of the alburnum, must therefore deter- 

 mine the age to which any tree can arrive. 

 * Wildenow. 



