Iso A TEXT-BOOK OF BOTANY 
spore-case. It has a long slender stalk, which becomes 
anchored in the stem of the leafy plant (Fig. 172); and the 
stalk bears an elaborate and usually urn-shaped spore-case 
full of spores (Fig. 173). This spore-case opens by means 
of a lid, which drops off; and often at the mouth of the 
urn thus opened there may be seen a set of delicate teeth 
extending from the margin of the rim and meeting in the 
center (Fig. 174). These teeth bend inward and outward 
as they are dry or moist, and help discharge the spores. 
It is evident that this spore-case with its anchored stalk is 
the sporophyte generation in the life-history. 
When the spores fall in suitable situations they germi- 
nate, and each one produces a green branching filament 
that looks like one of the filamentous green Alge (Fig. 
175). This branching filamentous growth spreads over the 
substratum, and presently there appear upon it buds 
(Fig. 175, B, 6), cach of which develops an erect leafy stem, 
which is recognized as a new leafy moss plant, the form 
with which this account of the life-history was begun. 
103. Alternation of generations.—In the life-history just. 
given, it is evident that the prostrate green filament and 
the erect leafy stems are two parts of the gametophyte; 
for the leafy stems simply arise as erect branches from the 
prostrate filament. It is strictly true, therefore, that the 
so-called moss plant, the conspicuous part of the moss, is 
aleafy branch of the gametophyte. These leafy branches 
become independent of the filament by sending out rhizoids 
into the substratum, so that it is only by actually germina- 
ting the spores that the filaments are seen. Not only does 
this branch bear leaves, and hence perform the chief work 
of food manufacture, but it also bears the sex-organs. 
The sporophyte, on the other hand, is dependent upon 
this leafy branch for its food-supply, and in that sense may 
be said to be parasitic upon it. Its only work is to produce 
spores; while the gametophyte does the chlorophyll work 
