8

THE PALM-STEM.

direction in the stem; but it must not be hence inferred that the vascularbundle of Palms is perfected in this direction in its formation; and in thefollowing pages I shall, according as it may be more conveniently stated,follow the vascular bundle, in the anatomical description, sometimes fromabove downward, and sometimes in the opposite direction.

The course of the vascular bundle is the same in allPalms, and the only distinctions which present themselvesare a difference of aspect at different points of the courseof the vascular bundle in different species.

In those species, for instance, which, like Kunthiamontana and Mauritia aculeata, possess firm woody vas-cular bundles only at the periphery of the stem, with acentre composed of soft, herbaceous substance, we findthat all the bundles are thin, soft, and herbaceous fromthe point where they enter the leaf, downward to thecentre of the stem, and from here outwards to the pointwhere they approach the outer hard, woody layer, and thatas they proceed downward in their course in that layer,they gradually become denser, and of a firm ligneous con-sistence. When the vascular bundles have reached theexternal part of this layer, and become situated beneaththe rind, their thickness is diminished, but not theirfirmness and hardness ; the latter peculiarity, however, isless remarkable, on account of their smaller diameter.They run in this manner, in the form of slender fibres,between the firm, woody layer and the rind, to the baseof the stem, or terminate, after a course of variable length,in other vascular bundles, becoming blended with them.As all the vascular bundles have a similar course, and theportion running in the middle of the stem is soft andherbaceous in all, the medulla-like softness of the centreof the stems is easily explained. It is also clear that thehardness of the outer layer of the stem results from thethickness and solidity acquired by the collective vascularbundles during their course through this outer layer;further, that the liber-like fibrous layer under the rind isformed by the lower extremities of the vascular bundles,and is not to be compared with the liber of Dicotyledons .