FERNS 193 
slide, and under a low power watching them as they dry 
and burst. 
110. Gametophytes.—In continuing the life-history of a 
fern, the spores when discharged, as just described, begin 
to germinate, provided they have reached suitable con- 
ditions. ach germinating spore produces a green thallose 
body that resembles a very small delicate liverwort 
(Fig. 186). It is deeply notched, having « gencral heart- 
shaped outline, and 
is usually — less 
than one-fifth of 
an inch in diame- 
ter. This thallus 
is so thin that. all 
its cells contain 
chloroplasts, and 
rhizoids from the 
under surface an- 
chor it to the soil. 
It is evident that 
it is an indepen- 
dent plant,  al- 
Fic. 186. -Gametophyte (prothallium) of a fern: 1, 
though a very under surface showing rhizoids (rh), antheridia (an), 
small one. Upon and archegonia (ar); B, under surface of an older 
. . gametophyte, showing the young sporophyte, with 
this minute plant root (w) and leaf (b).—After ScHENCK. 
the sex-organs are 
produced, and therefore it is the gametophyte in the life- 
history. This fern gametophyte, because it is a thallus 
body which precedes the appearance of the large sporo- 
phyte, has been called the prothallium (or prothallus), 
and this name has come to be very commonly used for 
gametophyte among all the higher plants. At the bottom 
of the conspicuous notch of the prothallium is the grow- 
ing point, representing the apex of the plant. 
The antheridia and the archegonia are produced on the 
