ORGANS OF NTTBITION. 77 



The following table is given by Lindley of the age of some 

 trees, all of which, he states, can be proved historically : — 



An Ivy near Montpelier . . . .433 years. 

 Lime trees near Fri burg . . . .1230 

 ,, ,, Neustadt .... 800 



Larch 576 



Cedars, on Mount Lebanon . . .6 — 800 

 Oaks at least 1000 



There can be no doubt, therefore, but that such trees will live 

 beyond the above periods. Other trees, such as the Wellingtonia, 

 Yew, and Olive, may be added to the above list; thus, it is probable 

 that the former will live at least 3000 years ; and it seems certain 

 that the Yew will attain the age of 1200 years, and the Olive at 

 least 800 years. 



Size of Trees. — As there is no assignable limit to the age of 

 exogenous trees in consequence of their mode of growth, so in 

 like manner the same circumstance leads, in many cases, to 

 their attaining great size. Thus the Wellingtonia gigantea has 

 been measured 116 feet in circumference at the base ; the 

 Chestnut {Castanea vesca) of Mount Etna is 180 feet in cir- 

 cumference ; a Plane tree {Platanus orientalis) near Constan- 

 tinople is 150 feet in circumference ; the Ceiba tree {Bombax 

 pentandrum) is said to be sometimes so large that it takes fifteen 

 men with their arms extended to embrace it ; even Oaks in this 

 country have been known to measure more than 50 feet in cir- 

 cumference ; and many other remarkable examples might be 

 given of exogenous trees attaining to an enormous size, which 

 circumstance is of itself also an evidence of their great age. 



Camhium-layer or Camhium, {Figs. 158, c, and 163, e.) — On 

 the outside of each annual zone (as we have already seen), a 

 layer of vitally active cells is placed, to which the name of 

 cambium-layer or carnhium has been given. It is from these cells 

 that the new layers of wood and bark are formed, and from the 

 fact of the cambium layer being situated on the outside of the 

 vascular bundles of which the wood is composed, these bundles 

 owe their continuity and indefinite power of increase. The cells 

 of which the cambium layer is composed are of a very delicate 

 nature, and consist of a thin wall of cellulose, within which is 

 situated a primordial utricle, a nucleus, and abundance of pro- 

 toplasm ; in fact, they contain all the substances which are 

 present in young growing cells. These contents were formerly 

 known under the name of cambium, and hence the origin of the 

 names cambium-layer and cambium applied to this portion of 

 the stem. This layer is dormant during the winter, at which 

 time the bark is firmly attached to the wood beneath, but it is in 

 fall activity in the spring, when it becomes charged with the ma- 



