ENDOGENOUS OR MONOCOTYLEDONOUS STEM. 



65 



sizes, often small in the vicinity of tlie vascular bundles, spiral 

 vessels or tracheae, t, large pitted vessels, v p, laticiferous vessels, I, 

 and bast fibres, /, resembling those of liber, thickened by internal 

 deposits. A similar section of a farther advanced endogenous stem, 

 as of a Palm (fig. 132), shows numerous bundles of vessels dispersed 

 irregularly in cellular tissue ; those near the centre, m, being scattered at 

 a distance from each other, while those towards the outside are densely 

 aggregated, forming a darkish zone, b, and are succeeded at the cir- 

 cumference by a paler circle of less compact vessels, I, with some com- 

 pressed cells, covered by an epidermis, e. The peripherical portion, I e, 

 differs from tnie bark, in not being separable from the rest of the tissue. 

 It has received the name of false bark, and consists of the epidermal 





v/i _ 



i^^'^iSP^ 



-*^. 



j^ 



Fig. 131. Fig. 182. 



cells, e, and what has been called the cortical integument, I. This 

 portion of the stem is often very inconspicuous, but sometimes it is 

 much developed, as in"Testudinaria elephantipes, in which it is rugged, 

 and is formed of a ^bstance resembling cork in many respects. 



Mohl states that in the stem of a Palm there may be distin- 

 guished a central region, a fibrous layer, and a cortical region ; and 

 the same divisions are pointed out by Henfrey in the stem of Spar- 

 ganium ramosum and other monocotyledons. The central portion, 

 representing the pith of dicotyledons, consists in Sparganium of 

 spherical cells, containing starch, while the cortical or outer portion 

 is formed by irregular cells, which are usually destitute of starch. 



It was at one time supposed that the woody portion of these 



Fig. 131. Horizontal section of a vascular bundle from tlie stem of a Palm {Corypha 

 frlgida). t, Trachese, or spiral vessels, v p, Large pitted vessels, u. Cells or utricles of 

 various kinds surrounding the vessels, and foi-ming the parenchyma, I, Laticiferous 

 vessels. /, Fibres analogous to those of liber, tihickened by concentric deposits. Fig. 182. 

 Transverse section of paxt of the stem of a Palm (As^ocarywn Murumura). m. Central or 

 meduUary portion, in which the woody bundles are distant and' scattered. 6, External 

 woody portion, where the fibres are numerous and densely aggregated, so as to form a dark 

 zone. I, Paler circle of more slender and less compact fibres, which may be considered 

 as analogous to liber, e. Cellular epidermal portion. 



E 



