22 THE PALM-STEM. 



mostly to be distinguished from these by their larger 

 cavity and somewhat thinner walls, and in the longi- 

 tudinal section by the septum being, at all events in the 

 vicinity of the vascular bundle, horizontal. This thicken- 

 ing occurs sometimes here and there in the outer bundles 

 of many Palm-stems, e. g. in Runtliia montana, in which 

 case it is met with in one vascular bundle and not in the 

 others ; or it is a structure occurring regularly in all 

 bundles, which, however, is only the case in Calamus. 

 Notwithstanding that there is here a great similarity 

 produced to the liber-cells by the thickening of the walls, 

 they may be distinguished from these by the somewhat 

 thinner walls, a larger cavity, as well as by the circum- 

 stance that, with the exception of the hindermost, they 

 are elongated in a direction parallel to the wall of the 

 large vessel. Their walls, like those of the liber-tubes, 

 consist of several layers, and possess pore-canals, which 

 are particularly striking in longitudinal sections, since 

 from their small distance from each other, the cell-wall 

 cut through possesses almost a moniliform aspect ; and 

 under these circumstances the nature of these canals, as 

 excavations perforating the cell-wall down to the outer- 

 most layer, may be recognised most clearly. 



The vessels of the Palms must be divided into the 

 large and small. Each of these kinds, as is clear from 

 what has been said already, occupies a definite place in 

 the vascular bundle. The large vessels, traced from the 

 lower fibrous extremity of the vascular bundle to its exit 

 into the leaf, do not anywhere exhibit the form of the 

 spiral, but that of the scalariform or reticulated vessel. 

 These vessels are composed of rather short tubes, standing 

 one above another. This composition may be perceived 

 even by the naked eye in the very wide vessels of Cala- 

 mus Draco, Mauritia vinifera, &c., the length of one of 

 the tubes in these plants amounting to 1 2 lines. The 

 face where the ends of the tubes meet one another is very 

 seldom horizontal, but mostly inclined considerably to- 

 ward the axis of the vessel. As a general rule, the ends 



