THE PALM-STEM. 41 



in the Palm-stem and in the one-year old shoot of the 

 Dicotyledons is exactly similar, and that the conception 

 of a different mode of growth, and the division of plants 

 into Endogens and Exogens formed on it, is altogether 

 opposed to nature. 



I have always found the structure of the yearling shoot of the Dicotyledons, 

 such as I have described ; 1 cannot, therefore, agree with the description 

 given by Schweigger (Beobacht. auf naturhist. Reisen, 107), which goes to 

 show that in the Dicotyledons the upper leaves are supplied by the internal, 

 the lower by the external vascular bundles. 



In spite of this resemblance, we must not overlook the 

 fact, that very important differences occur in the organiza- 

 tion and growth of Dicotyledons and Monocotyledons. In 

 the yearling stems of a Dicotyledon, the vascular bundles 

 going to the higher leaves are interpolated in their lower 

 part, between the liber and wood of the older. The wood 

 of the younger thus becomes blended with that of the 

 older, while in many cases the liber-bundles of these 

 remain isolated. From this cause, the wood in the lower 

 part of the stem becomes thicker, and the entire stem 

 acquires a conical form. In the Palms, on the contrary, 

 in the vascular bundles of which the liber and wood stand 

 in the closest connexion, the lower parts of the younger 

 bundles are never interposed between the wood and liber 

 of the old, but lie isolated in the cellular tissue of the 

 stem, nearer to the periphery than the older bundles. 

 Thus neither the liber nor wood of the older bundles 

 exhibit a deposition of new portions, but remain perma- 

 nently in that stage of development, which they have 

 attained at their original completion. 



We must not consider it as an universal distinction, that in the Monocoty- 

 ledons the vascular bundles do not unite laterally into a reticulation, since, 

 on the one side, in Dracana, Aletris, &c., the fibrous bundles of the outer- 

 most layers become connected together in this way, and on the other hand, 

 in some of the herbaceous, and even in many woody Dicotyledons, for in- 

 stance, in Rosa and Rubus, this lateral connexion of the vascular bundles 

 does not exist. 



The phenomenon that the Palm-stem grows but little 



