84 A LABORATORY MANUAL OF BOTANY 
and the covering (operculum) of the mouth? Of what use 
are these structures? 
These asexual spores fall, after which they grow, pro- 
ducing protonema, and begin another life cycle. Since this 
latter phase of the plant produces the asexual spores, it is 
called the sporophyte (spore plant). 
General suggestions.—It is noted that in this plant we 
have one phase producing spores by means of gametes, and 
another producing them asexually. These two phases are 
called the gametophyte and sporophyte generations respect- 
ively, and as each one produces a spore which develops the 
other we have alternation of generations. In this case one 
generation never produces both kinds of spores. 
In what respect are mosses more complex in their repro- 
duction than Alge and Fungi? Does the way the proto- 
nema lives have anything to do with the wide distribution 
of mosses? How is the leafy moss shoot better fitted for 
nutritive work than such Alge as Vaucheria and Spirogyra? 
Is the position of the stem of any especial significance? 
Does a moss need any greater supporting power than an 
alga? Any greater power of carrying materials? 
LESSONS XLVIII AND XLIX 
A liverwort—Marchantia! 
The liverworts usually live in shady, secluded places, 
although some may be exposed to direct sunlight. They 
generally have prostrate bodies, that bear rhizoids on their 
lower surface. Sometimes they have leaf-like expansions 
from the main axis of the body. The latter are called the 
leafy liverworts, the former the thallose liverworts. 
1Tn order of development liverworts precede mosses. The mosses, 
however, illustrate more clearly the alternation of generations, and 
through them the liverworts are more easily understood. 
