114 



EVOLUTION OF PLANTS 



phases, the protonema and gametophore. The spore 

 on germination produces a filamentous, or occasionally 

 flat, alga-like growth, the protonema (Fig. 29, A, B, C, 



jt?r), and upon this 

 arise special buds or 

 branches which grow 

 into leafy stems, the 

 gametophores (Fig. 29, 

 A, B, C, &), which bear 

 the sexual organs. The 

 leaves of the gameto- 

 phoric branches are 

 commonly arranged 

 spirally, and the 

 branches seldom are 

 flattened as in the 

 foliose Hepaticse. 

 While there are cer- 

 tain superficial resem- 

 blances between the 

 leafy stems of the 

 mosses and foliose 

 liverworts, there are 

 differences which make 

 it extremely improb- 

 able that the former have been derived from the latter; 

 The two forms are rather to be considered as parallel 

 developments. In the Musci the structure of both leaves 

 and stem is as a rule much more complex than in the 

 Hepaticse, and there is usually present a central strand 

 of conducting tissue, quite wanting in both stem and 

 leaf in the latter group. 



'Pr 



FIG. 29 (Musci or True Mosses). A, the 

 liverwort-like protonema of a peat- 

 moss (Sphagnum) with the leafy shoot, 

 k, budding out from it ; B, the fila- 

 mentous protonema, pr, of a common 

 moss (Funaria), with a very young 

 leafy bud, k ; C, an older stage of the 

 same moss; D, the full-grown leafy 

 gametophore, g, with the sporophyte, 

 sp, still connected with it ; ar, the re- 

 mains of the archegonium carried up 

 by the growth of the sporophyte. 



