SPORANGE OF MOSSES 



673 



which consists of the leafy pLmt bearing the male and female organs ; 

 and the non-sexual generation or ' sporophyte,' composed of the 

 sporogone with its spores, these two generations alternating with one 

 another in the complete cycle of development. 



The tribe of Sphagnacece, or 'bog-mosses,' is now separated by 

 muscologists from true mosses mi account of the marked differences 

 by which they are distinguished, the three groups, lL:>j>nti<'<i\ 

 Bryacece (or ordinary mosses), and Sphagnacece, being ranked as to- 

 gether forming the group of Muscinece. 

 The stem of ,s'////"///>mw is more dis- 

 tinctly differentiated than that of 

 lirt/acfd' into the central or medullary, 

 the outer or cortical, and the inter- 

 mediate or woody portions: and a very 

 rapid passage of fluid takes place 

 through its elongated cells, especially 

 in the medullary and cortical layer.--,, .so 

 that if one of the plants be placed dry 

 in a flask of water, with its rosette 

 of leaves bent downwards, the water 

 will speedily drop from this until the 

 flask is emptied. The leaf-cells of the 

 Sphagnacea exhibit a very curious de- 

 parture from the ordinary type ; for 

 instead of being small and polygonal, 

 they are large and elongated (fig. 514) ; 

 they contain no chlorophyll, but have 

 spiral fibres loosely coiled in their in- 

 terior ; and their membranous walls 

 have large rounded apertures, by which 

 their cavities freely communicate with 

 nne another, as is sometimes curiously 

 evidenced by the passage of wheel- 

 animalcules that make their habitation in these chambers. -Between 

 these coarsely spiral cells are some thick-walled narrow elongated 

 cells containing chlorophyll; these, which give to the leaf its firm- 

 ness, do not, in the very young leaf, differ much in appearance from 

 the others, the peculiarities of both being evolved by a gradual pro- 

 cess of differentiation. The aiitherids, or male organs, of S]>Ji(i</nin-<-(i 

 resemble those of liverworts, rather than those of mosses, in their 

 form and arrangement; they are grouped in 'catkins' at the tips 

 of lateral branches, each of the imbricated perigonal leaves enclosing 

 i single globose antherid on a slender footstalk, and they are sur- 

 rounded by very long branched paraphyses of cobweb-like tenuity. 

 The female organs, or archegones, which do not differ in structure 

 from those of mosses, are grouped together in a sheath of deep green 

 leaves at the end of one of the short lateral branchlets at the side of 

 the rosette or terminal crown of leaves. The two sets of organs 

 are always distributed 011 different branches, and in some inMance.s 

 on different plants. The sporange ' which is formed as the product 

 of the impregnation of the germ-cell is very uniform in all the 



x x 



FIG. 514. Portion of the leaf of 

 Sphagnum, showing the lar^e 

 empty cells, , a, , with spiral 

 fibres, and communicating aper- 

 tures; and the intervening 

 bands, b, b, b, composed of 

 small elongated chlorophyllous 

 cells. 



