266 PRINCIPLES OF BOTANY, ETC. 
advances in age, the browner and darker grows the 
bark ; it cracks, and the functlon of expiration can- 
not go on as before, nor are the vessels in the cuticle 
any longer visible. Some trees and shrubs lose 
their bark annually, and reproduce a new'one from 
the inner bark. As instances may be given, the 
Platanus occidentalis, and the Potentilla fruticosa. 
The age of a tree or shrub may be easily deter- 
mined by the number of these heneous circles, upon 
cutting the stem through, close to the root. In the 
same manner the main root shews most accurately 
the age by its ligneous circles, when cut directly be- 
low the surface of the ground. 
In the Palmae, however, according to Daubenton’s 
observation, this is very different. For if we cut a 
stem horizontally through, we find no difference be- 
tween an old or young tree. In them the vascular 
bundles don’t dispose themselves in a circular form. 
They consist of vessels running in a straight line, 
without regular order, and inclosed by a cellular 
membrane. Nor do they grow thicker annually 
or possess proper bark, but this is formed by the 
remnants of the leaves. Daubenton is not inclined 
to assion the name of wood to their substance, 
and proposes, if it were to be given to their 
fibrous substance, the name of Jignum fasciculatum, 
to distinguish it from the common wood, which he 
calls /ignum reticulatum. ‘As the Palmae are desti- 
tute of branches, their leaves arise not from buds, 
but are in fact only small separated bundles of ves- 
sels of the steni, which expand in a leafy form. 
3 Hence 
