TJ1E PALM-STEM:

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old stein, the condition was different, the greater numberof their vascular bundles being lost in the outer woodylayers of the stem, only solitary fibres curving upwardsor downwards, to run further beneath the rind. In theroots of many other arborescent Monocotyledons he con-stantly saw the vascular bundles, if the root were stillyoung, spread out like a star over the woody layer of thestem; in older roots, on the contrary, they penetrateddeeper into the stem, where they then ramified and lostthemselves. Meneghini derives these differences fromthe different conditions of the course of the sap; themain root (tap-root) and the lowest roots of the stem areformed at the same time, and with the help of the samecurrents of nutrient sap, as the vascular bundles of thestem, the latter, therefore, pass directly into the fibres ofthe former; but when roots are formed on the olderparts of the stem, the currents of sap cause a stellateexpansion of their vascular bundles on the surface of thewoody mass of the stem.

Unger has given some contributions to the knowledgeof the Monocotyledonous stem, having, in his researcheson the Dicotyledonous stem (Ueber den Bau und dasYVachsthum des Dicotyledonenstammes, 1840, p. 35),taken a comparative glance at the structure of the Mono-cotyledons, and, more particularly, subjected the stem ofthe Aloineai ( Draceena , Aletris, Yucca , Agave) to a moreminute investigation. With regard to the course andanatomical peculiarities of the vascular bundles, Ungeragrees in general with the description I have given, andthus nothing need be said on this point. But from hisinvestigation of the course of development of the vascularbundles, he has been led to propound a definite opinionas to the import of their proper vessels, while I had letthis point remain untouched. He traced the develop-ment of the vascular bundles principally in the Aloinece,and states that their rudiments are uniformly cellular, thatthe other systems (the wood and liber portions) maketheir appearance subsequently at the inner and outer