THE PALM-STEM.

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perceived most clearly when a longitudinal section passesthrough the adjacent walls of two scalariform ducts, inwhich case we recognise distinctly that the slits are actualexcavations in the walls of the vessels, and not elevations,as stated by Bernhardi (Ueber Pflanzengefasse, p. 35),Treviranus (Beitrage, p. 22), and Meyen (Pliytotomie,p. 253), but that the interspaces between the slits formelevations which project into the vessel. It may likewisereadily be perceived that a membrane is stretched betweenthe fibres, separating the fibres of the two vessels underthe from of a simple, dark line. The development ofthese vessels shows that this membrane forms a tubeinclosing the fibres. The pores and slits equally exhibitan evident rim, which does not depend, as Mirbel assumes,on the presence of a projecting border, but is, on the con-trary, caused by the borders of the slit being truncatedby an oblique surface.

In many cases, as in Calamus for example, the placewhere two vascular tubes are connected is conspicuous,from each tube ending in a broad ring; the two adjacentrings form a band surrounding the vessel, as Moldenliawerhas shown long since in other plants. When the tubesmeet by such a ring, they are freely open to each other.In other cases, on the contrary, particularly in Desmoueusmitis, Cocos nucifera , Mauritia vinifera, armata, Kunthiamontana, Astrocaryum yynacanthum, vulgare, Corypha fri-yida, wo such rings are seen at the points of connexion of thetubes, and in these are found septa. The existence ofsuch septa is indeed denied utterly by all phytotomists;but having observed them hundreds of times, not only inthe Palms, but in many other Monocotyledons, and evenin many cases in the porous vessels of Dicotyledons , I donot hesitate to assert their existence in the most positivemanner. The direction of these septa is usually suchthat we obtain a front view of them in a longitudinalsection made in the direction of the radius of the stem.They differ completely from all other membranes of plants,in being formed of a reticulation of thick fibres, withlarge openings between them. In the stems of Palms