122 



PLANT STRUCTUKES 



a rosette, in the center of which are the sex organs. This 

 rosette is often called the ^^moss flower," but it holds no 

 relation to the flower of Seed-plants, and the phrase should 

 not be used. A rosette may contain but one kind of sex 

 organ (Figs. 83, 103), or it may contain both kinds, for 

 Mosses are both dioecious and monoecious. The two prin- 

 cipal groups are as follows : 



73. Sphagnum forms. — These are large and pallid bog 

 mosses, found abundantly in marshy ground, especially of 

 temperate and arctic regions, and are conspicuous peat- 

 formers (Fig. 105, A). The leaves and gametophore axis 



are of peculiar struc- 

 ture to enable them 

 to suck up and hold 

 a large amount of wa- 

 ter. This abundant 

 water - storage tissue 

 and the comparative- 

 ly poor display of 

 chlorophyll - contain- 

 ing cells gives the 

 peculiar pallid ap- 

 pearance. 



They resemble the 

 Liverworts in the 

 broad thallus body 

 of the gametophyte, 

 from which the larg3 

 leafy gametophore 

 arises (Fig. 104). 

 They also resemble 

 Anthoceros forms in the sporogonium, the archesporium 

 being a dome-shaped mass (Fig. 105, C). On the other 

 hand, they resemble the true Mosses, not only in the leafy 

 gametophore, but also in the fact that the capsule opens 

 at the apex by a circular lid, called the operculum (Fig. 



Fig. 104. Thallus body of gametophyte of Sphag- 

 num, giving rise to rhizoids (r) and buds (k) 

 which develop into the large leafy branches 

 (gametophores).— After Campbell. 



