300 CONSERVATIVE ORGANS. [LECT. VII. 



b. The hollow or fistular monocotyledonous 

 stems are composed of distinct portions, united by 

 knots ; at each of which the cavity is divided by a 

 diaphragm : or, rather, each portion may be re- 

 garded as a distinct individual, which takes its 

 origin from one knot, and terminates in another, 

 out of which again a new individual arises, and so 

 on in succession, as I shall more particularly de- 

 scribe in explaining the mode of growth of these 

 stems. The general structure of this description 

 of stems is best exemplified in the Grasses. Thus, 

 in Wheat we perceive the upper articulation rising 

 within the knot, in which the lower has termi- 

 nated ; with the leaf which infolds it crowning 

 the embracing knot*. The organization of this 

 variety of the monocotyledonous stem cannot be 

 readily distinguished without the aid of the mi- 

 croscope. It is seen, in a longitudinal section, to 

 consist of several layers of narrow oblong cells, 

 which constitute its exterior and more solid part ; 

 and of an interior more open cellular substance, 



the vascular cords and the inosculation of the vessels, a. The 

 bed or sheath in which the vessels run ; b. the vessels themselves 

 apparently composed of separate rings, held together by small 

 spicular bodies, which appear as lines on the surface of the 

 vessels, within the transparent sheaths ; when detached, they 

 appear like acicular crystals. The cells are studded with amy- 

 laceous granules. 



* Vide Plate 5, fig. 1 1. a. the knot of the straw bearing a 

 fragment of its leaf; b. the new articulation rising within the 

 knot. 



