THE PALM-STEM.

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parts. The youngest portion of the stem is frequentlyclothed with a hair-like covering, so long as it is stillyoung and inclosed by the leaf-sheaths. Sometimes thisappears in the form of actual hairs, which are mostlyclosely crowded and coherent into a dense felt; e. g. inBadris tomentosa. In other cases, the covering is com-posed of scales ( ramenta ), which exactly resemble thoseof the Ferns ; e. g. in Bhapis Jlabelliforniis, Phoenixdadylifera. In other instances the cells are combinedinto spines of various dimensions. On the leaf-slieathsand spathes many transitional forms are met with, fromsimple hairs, stiff bristles, to strong, hard spines. Spinesof this kind exist on the stems of many Palms, lyingclosely appressed to it, so long as the intern odes are in-cluded in the leaf-sheaths; but erecting themselves afterthe fall of the leaf, they form a terrible defence to the stemby their hardness, length, and prickly points.

The spines are sometimes blunt cones, but about aninch long, as in Mauritia armata; in Acrocomia sclero-carpa, Astrocaryum Murumuru, Ayri, yynacanthum, &c.,on the contrary, they form long, slender, very hard andacute needles. These are only cellular structures; thecells of the outer layers are elongated, hard, and havevery thick walls, those in the middle are thin-walledand parenchymatous; the middle of the spine is oftenhollow.

Structure of the Vascular Bundle .

Before I describe the modifications which the structureof the vascular bundle undergoes in the different parts ofits course, it may not be out of place to state its com-position in those situations at which, from the hard peri-pherical cylinder of wood, it enters, on its way to thecentre, the soft middle substance of the stem. It hereconsists of three constituents, which may be clearly dis-tinguished from each other: 1, of liber; 2, of a bundleof proper vessels ( vasa propria) ; and 3, of the ligneous