MOSSES, LIVERWORTS, AND FERNS 275 



toward the antheridia. The enlarged part of an archego- 

 nium, where the egg is formed, is imbedded. The neck opens, 

 sperms enter, and one of the sperms unites with the egg. The 

 result is the formation of an oospore, which is inclosed in the 

 tissue. Since this heart-shaped plant produced the sex cells, 

 it is the gamete plant, or gametophyte, and since the asexual 

 spores are formed upon the leafy fern plant, that is the spo- 

 rophyte. The asexual spore germinates and produces the ga- 

 metophyte, and the oospore germinates and produces the leafy 



FIG. 213. Fern antheridium, with sperms FIG. 214. Archegonium of a f ern 

 Greatly magnified Greatly magnified 



sporophyte. The young leafy plant at first appears as if it grew 

 directly from the heart-shaped gametophyte (fig. 212). It soon 

 develops leaves and roots and an underground stem in short, 

 is a new leafy fern plant. 



It must be clear that in ferns there is the same kind of alter- 

 nation between the sexual and asexual generations of the plant 

 as that seen in the mosses, except that in the ferns each stage of 

 the plant lives for a time quite independent of the other stage. 



260. Significance of fibrovascular tissue. It is evident that 

 a fern leaf exposes much chlorophyll to the light much 

 more than does any plant among the bryophytes. The strong 

 supporting and conducting tissues of the leaf uphold the 



