286 ESSENTIALS OF BOTANY 
is shown in the diagram (Fig. 208). In the mosses and 
their allies the full-grown plant is a gametophyte, and the 
spore-bearing plant or sporophyte appears as a sort of par- 
Fic. 209. Sensitive Fern (Onoclea). 
s, sterile or vegetative frond; /, fertile frond 
or sporophyll. 
asitic outgrowth of the 
gametophyte (Sect.357). 
‘In the ferns and their 
allies the full-grown 
plant (that which we com- 
monly call a fern) is an 
asexual sporophyte, am- 
ply provided with vege- 
tative organs, 7.e. roots, 
stem, and leaves, often 
capable of living for 
many years and attain- 
ing the dimensions of a 
tree. The gametophyte 
(prothallium) in ferns is 
a minute, usually short- 
lived structure, and ex- 
ists simply to mature an 
egg which may produce 
a fern-plant. 
366. Summary of the 
Ferns. — Most ferns are 
land plants, but there 
is one order of aquatic 
ferns, some of which live 
floating freely in water and others grow rooted in the 
mud. Ferns vary greatly in size, the smallest genera not 
being nearly as large as some mosses, while others are tree- 
like. With abundant vessels, rigid tissue for strengthening 
