STKUCTURE OF MOSSES 



669 



Musci. There is not one of the tribe of J losses whose external 

 organs do not serve as beautiful objects when viewed with low powers 

 of the microscope ; while their more concealed wonders are ad- 

 mirably fitted for the detailed scrutiny of the practised observer. 

 Mosses always possess a distinct axis of growth, commonly more or 

 less erect, on which the minute and delicately formed leaves are 

 arranged with great regularity. The stem shows some indication of 

 the separation of a cortical or external portion from the medullary 

 or central, by the intervention of a circle of bundles of elongated 

 cells, which seeni to prefigure the woody portion of the stem of 



FIG. 508. Structure of mosses : A, plant of Fiinaria li ijgrometric a, showing, / the 

 leaves, it the sporanges supported upon the setiw or footstalks .s, closed by the opercule 

 o, and covered by thecalypter c. B, sporanges of Eimiiyjitra vulgaris, one of them 

 closed and covered with thecalypter, the other open ; u, n, the sporanges; o, o, the 

 opercules ; c, calypter ; p, peristome ; s, s, seta?. C, longitudinal section of very 

 young sporange of Splacknwn ; a, solid tissue forming the lower part of the capsule ; 

 f, columel ; I, space around it for the development of the spores ; r, epidermal 

 layer of cells, thickened at the top to form the opercule <> ; j>, t\vo intermediate 

 layers, from which the peristome will be formed; s, inner layer of cells forming 

 the wall of the cavity. 



higher plants, and from which prolongations pass into the leaves, so 

 as to afford them a sort of midrib. The leaf usually consists of either 

 a single or a double layer of cells, having flattened sides by which 

 they adhere one to another ; they rarely present any distinct 

 epidermal, layer ; but such a layer, perforated by stomates of sipmle 

 structure, is commonly found on the seta or bristle-like footstalk 

 bearing the fructification, and sometimes 011 the midribs of the leaves. 

 The rhixoids of mosses, like those of Marchantia, consist of long 

 tubular cells of extreme transparency, within which the protoplasm 

 may frequently be seen to circulate, as in the elongated cells of 

 Char a. 



