90 



ORGANOGRAPUY. 



Fig. 178. 



'^Skd 



'^t^^ 





Fig. 178. 1. Unbranched stem of the Cocoa-nut Palm (Cocos titir.ifcra). 2. 

 Branclied stem of Pandamis odoratissimus. The figures are placed at 

 their base to indicate their height. From Jussieu. 



as to form zones of wood, as in exogenous stems {figs. 164, /^ 

 and 1 79, b, c, d). The wliole is covered externally by a fibrous 

 and cellular layer, called the /a/.se bark or rind {fig. 164, i); 

 but such is not a distinct and ])arallGl fornuxtion to the wood as 

 the bark of Kxo;rens, but it is formed by the ends of the vascular 

 bundles, as will be presently noticed, and cannot therefore be 

 separated from the mass l)eneath. In herbaceous endo<;cnous 

 stems the general cellular or medtiUary substance between the 

 vascular bundles is soft and delicate, but in such trees as the 

 Palms, &c., the cells become hardened by the deposition of 

 secondary layers upon their inner surfaces, thus forming what 

 has been termed tvoodi/ parenclit/ma, which ultimately binds the 



