LECT. VII.] ANATOMY OF STEMS. 297 



of the herbaceous they form irregular hexagons, 

 except towards the circumference, and in the 

 immediate vicinity of the vascular cords*; and 

 that the membrane forming them is perforated 

 with minute pores, surrounded by a glandular 

 border. In the common Rush, Juncus conglo- 

 meratus, and some other monocotyledons, the 

 cells of the pith are of a very curious structure : 

 appearing, in a transverse section, like minute 

 heptagonal wheels or circles divided by rays 

 passing from the centre ; and these are evidently 

 filled with air *f-. In common MareVtail, Hip- 



* Vide Plate 5. Fig. 3, B. represents a magnified section 

 of fig. 3, A. to demonstrate the greater density of the cellular 

 substance towards the circumference. 



Fig. 5, B. a highly magnified section of fig. 5, A. a. the 

 cellular substance more condensed close to the epidermis 

 than in the heart of the stem ; b. the vascular bundles. Fig. 

 5, C. a highly magnified longitudinal section of the semi- 

 diameter of the slice A. which has the appearance of fig. 5, 



d. to the naked eye: a. the cellular matter, close to the 

 epidermis, appearing as oblong cells ; I. one of the seemingly 

 solid cords, which form the circle of vascular bundles, con- 

 sisting of two spiral vessels, surrounded by oblong cells; 



e. the cellular substance which constitutes the mass of the 

 stem. In this view the membrane forming the walls of the 

 cells is seen studded with points, which, under the microscope, 

 appear to be either amylaceous granules or circular apertures 

 surrounded by a border. Mirbel supposes they are pores, and 

 that the border is glandular. 



f Vide Plate 5, fig. 6, which represents a magnified section 

 of a transverse slice of the common Rush : a. the pith com- 



