LECT. X.] ANATOMY OF LEAVES. 551 



The vessel itself is closely connected with the 

 cellular matter, and when separated (see 2, a 

 highly magnified representation), bears the marks 

 of the cells on its sides. We find nearly the same 

 vascular structure in the Mosses. Thus, if we 

 take a leaf of broad-leaved Bog-Moss, Sphagnum 

 obtusifolium. as a specimen, we find it, when 

 magnified as at 3 (b. shows the natural size of the 

 leaf), consisting of a midrib (a.), on each side of 

 which are many oblong cells, arranged apparently 

 in straight lines : but, under the microscope, these 

 oblong cells are seen to consist of elevated cuticle 

 (as at 4. b. b. b. b. b.) in the meshes of a reticulated 

 vascular system (4. a. a. a. a.) 3 too minute to al- 

 low of the nature of the vessel to be made out by 

 the aid of the highest magnifying powers. It 

 is probably the same as that of the vessels of 

 Marchantia. The leaves of all the Mosses are 

 sessile, although many of them are sheathing; 

 and most of them are furnished with a midrib; 

 but their minuteness prevents any certain informa- 

 tion being obtained as to the manner in which the 

 leaves receive their vessels from the stem, or 

 whether there be a distinct set of returning 

 vessels : they appear to be merely a continuation 

 of the vessels of the cortex of the stem. Sprengel 

 asserts that in the Sphagnum before us, both the 

 cells of the leaf and those on the surface of the 



N N 4 



