THE PALM -STEM. 37 



in a circle, and are separated from each other by strips 

 of parenchymatous cells varying in breadth ; the vascular 

 bundle of Laserpitium aquilegifolmm may serve as an 

 example. We find in this a great quantity of irregu- 

 larly distributed vessels, the larger of which lie toward 

 the outside, the smaller toward the interior ; the exterior 

 vessels are porous and scalariform ducts, the deeper-lying 

 ones spiral vessels. The cellular tissue in which the 

 vessels are imbedded, consists of thin-walled, elongated 

 cells, and narrow, thick-walled cells are only met with in 

 the outermost parts of the ligneous body. The most pos- 

 terior or internal part of the vascular bundle also contains 

 thick- walled cells. In front of the vascular bundle lies a 

 bundle of liber-cells, which is connected by a process on 

 each side with the wood bundle ; between the wood and 

 the liber lies a bundle of proper vessels. It is here clear 

 that this vascular bundle has entirely the same structure 

 as the Monocotyledonous bundle, the only distinction that 

 occurs being, that the woody mass is gradually increased 

 in size by the deposition of new layers on its outside. 

 The relations of the vascular bundle to the surrounding 

 parenchyma are likewise identical with those which are 

 found in the Monocotyledons furnished with an outer 

 ring of thick-walled cells. The large thin-walled paren- 

 chymatous cells of the stem, which send broad processes 

 corresponding to the medullary rays, between the vas- 

 cular bundles to the bark or rind, acquire thicker walls 

 between the anterior portions of the vascular bundle, and 

 approach pretty closely in form to the liber-cells. 



If we examine the young shoot of Aristolockia Sipho, 

 we find here also a great similarity of the vascular bun- 

 dles to those of the Dicotyledons,* the woody mass con- 

 sisting of a thin-walled parenchyma, the cells of which 

 do not lie in any definite order. In the back part of the 

 vascular bundle are found minute spiral vessels ; in front, 

 large porous vessels. It is only in front of these large 



* Q,y. misprint for Monocotyledons. TRANS. 



