30 THE PALM-STEM. 



is traced upward to the point where it displays itself as a 

 perfect vascular bundle, they show themselves sooner than 

 the woody mass itself. However, this earlier develop- 

 ment relates only to space and not to time. I do not 

 venture to give an opinion as to the function of this sys- 

 tem, and for the present am content to have demon- 

 strated their existence anatomically. 



Comparison of the Palm-stem with the stems of other 

 Monocotyledons. 



With regard to the course of the vascular bundle, the 

 Palms stand nearest to Dracana, Aletris, and Aloe ; with 

 reference to the organization of the bundle, to the Grasses. 



As to the structure of the vascular bundle of the 

 Grasses, I refer to the excellent researches of Moldenhawer, 

 and merely mention here, that in the Grasses the vascular 

 bundle not only increases in size from the periphery to- 

 ward the centre of the stem, but its structure is altered 

 at the same time, in a manner analogous to what occurs 

 in the Palms. Beneath the surface of the stem we meet 

 with fibrous bundles without vessels, then fibrous bundles 

 containing a bundle of proper vessels, and these are 

 adjoined by vascular bundles with reticulated vessels, 

 while small vessels occur, in addition, in the inner. The 

 perfect vascular bundles, for example, of Arundo Donaoc, 

 contain two large vessels surrounded by thin-walled wood- 

 cells, behind these lie a row of two or three small vessels ; 

 the hindmost portion of the wood-cells is composed of a 

 mass of thick-walled, dotted prosenchyma, as also fre- 

 quently occurs in the leaves and other organs of the 

 Palms. Between the wood and the liber lies a bundle of 

 proper vessels, the large cells of which are mostly qua- 

 drangular, and have a narrower cell lying between their 

 angles. 



In Dractena and Aloe, the former of which is especially 

 interesting on account of the minute researches on its 



