36 THE PALM-STEM. 



bundles together with it. From these reasons it is inadmissible, although 

 Link (Grundlehren, p. 143 ; Elem. Phil. Bot. p. 140) explains this ring as 

 liber, a view which Kieser also propounded (Phytot. p. 72). This ring is 

 very sharply denned at its outer side, and surrounded by parenchyma which 

 represents the bark. 



I have already expressed rny opinion that the proper vessels lying in the 

 vascular bundles are not to be reckoned as belonging to the milk-vessel 

 system, in which the so-called vital sap is contained in Chelidonium, Asclepias, 

 Euphorbia, Musa, Fic^ts, &c. This is clear from the fact that the vital-sap 

 vessels do not occur in the place in which these proper vessels lie in the 

 Monocotyledons, for the former lie isolated in the interspaces of the cellular 

 tissue, chiefly in the vicinity of the vascular bundles, in the pith and the 

 bark. But it is best proved by the existence of many Monocotyledons, in 

 which both these kinds of vessel are met with, independently, each in its 

 proper place, and in these cases the two kinds of vessel conveying wholly 

 different sap. Thus it is known, for example, from Moldenhawer's 

 researches (Beitrage, p. 134), that milk-vessels lie in the parenchyma in the 

 vicinity of the vascular bundles in Miisa, the sap of which, like that of 

 Sambucus, assumes a red colour, and which was also recognised as vital sap 

 by Schultz (Natur. d. leb. Pfl. i, 537). These vessels, then, are distinguished 

 from the proper vessels in the vascular bundles by their different situation 

 and by the red colour of their contents, which colour is never assumed by 

 the sap of the proper vessels. The proper vessels in the vascular bundle of 

 Sagittaria are no less clearly distinguished from the milk-vessels lying scat- 

 tered in the parenchyma of the peduncle and petiole, for the latter convey a 

 milky, the former a very transparent sap. In Alisma Plantago, likewise, the 

 vessels filled with milky juice are wholly detached from the vascular bundles. 



Comparison of the Vascular Bundle of the Palms with 

 that of the Dicotyledons. 



In order to place in a clearer light the connexion of the 

 organization of Palms with that of the Dicotyledons, and 

 in order to state more accurately the grounds on which I 

 have called the different parts of the vascular bundle of the 

 Palms, liber and wood, a comparison of the vascular 

 bundle of the Palms with that of the Dicotyledons be- 

 comes necessary, since in the latter alone can there exist 

 no doubt as to the true import of its parts. 



In herbaceous Dicotyledons the vascular bundles stand 



