MOSSES, LIVERWORTS, AND FERNS 276 
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 odspore, 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 odspore germinates and produces the leafy 
Fig. 213. Fernantheridium, withsperms Fre. 214. Archegonium of a fern 
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 
