36

THE PALM-STEM.

bandies together with it. From these reasons it is inadmissible, althoughLink (Grundlehren, p. 143; Elem. Phil. Bot. p. 140) explains this ring asliber, a view which Kieser also propounded (Phytot. p. 72). This ring- isvery sharply defined at its outer side, and surrounded by parenchyma whichrepresents the bark.

I have already expressed my opinion that the proper vessels lying in thevascular bundles are not to be reckoned as belonging to the milk-vesselsystem, in which the so-called vital sap is contained in Chelidonium, Asclepias,Euphorbia , Musa, Ficus , &c. This is clear from the fact that the vital-sapvessels do not occur in the place in which these proper vessels lie in theMonocotyledons, for the former lie isolated in the interspaces of the cellulartissue, chiefly in the vicinity of the vascular bundles, in the pith and thebark. But it is best proved by the existence of many Monocotyledons, inwhich both these kinds of vessel are met with, independently, each in itsproper place, and in these cases the two kinds of vessel conveying whollydifferent sap. Thus it is known, for example, from Moldenhawer’sresearches (Beitriige, p. 134), that milk-vessels lie in the parenchyma in thevicinity of the vascular bundles in Musa, the sap of which, like that ofSambucus , assumes a red colour, and which was also recognised as vital sapby Schultz (Natur. d. leb. Pfl. i, 537). These vessels, then, are distinguishedfrom the proper vessels in the vascular bundles by their different situationand by the red colour of their contents, which colour is never assumed bythe sap of the proper vessels. The proper vessels hi the vascular bundle ofSagittaria are no less clearly distinguished from the milk-vessels lying scat-tered in the parenchyma of the peduncle and petiole, for the latter convey amilky, the former a very transparent sap. In Alisma Plantago, likewise, thevessels filled with milky juice are wholly detached from the vascular bundles.

Comparison of the Vascular Bundle of the Balms withthat of the Dicotyledons .

Tn order to place in a clearer light the connexion of theorganization of Palms with that of the Dicotyledons , andin order to state more accurately the grounds on which Ihave called the different parts of the vascular bundle of thePalms , liber and wood, a comparison of the vascularbundle of the Palms with that of the Dicotyledons be-comes necessary, since in the latter alone can there existno doubt as to the true import of its parts.

In herbaceous Dicotyledons the vascular bundles stand