SOME TYPES OF FLOWERLESS PLANTS. 235 
partnership which occurs both among plants and among 
animals. The so-called lichen is really a complex colony 
composed of a multitude of minute fungi living in close 
connection with certain thread-like alge. The partnership 
between the two kinds of plants is not an especially one- 
sided affair ; though the alge are the principal breadwinners 
of the firm, their association with the fungi enables them to 
live in situations and under conditions that would be fatal to 
the algze alone. 
290. Reproduction in Fungi. — The reproductive processes 
in fungi are so various in their character, and involve so 
much microscopical study, if they are to be clearly under- 
stood, that it would require many chapters to describe them. 
The examples already considered in the cases of yeast and 
the moulds must be allowed to stand as representatives of 
the great number of interesting types that offer themselves to 
the student of this department of cryptogamic botany. 
THE STUDY OF PIGEON-WHEAT MOSS.! 
291. Occurrence. — This moss, Fig. 202, is widely distributed over 
the surface of the earth, and some of its species are among the best- 
known mosses of the northern United States. Here it grows commonly 
in dry pastures or on hillsides, not usually in densely shaded situations. 
292. Form, Size, and General Characters. — Study several specimens 
which have been pulled up by the roots.2 Note the size, general form, 
color, and texture of all the parts of the plants examined. Some of them 
probably bear urns or spore-capsules like those shown in Fig. 202, while 
others are without them. Sketch one plant of each kind, about natural size. 
What difference is noticeable between the appearance of the leaves in 
those plants which have spore-cases and those which have none? Why 
is this ? 
1 Polytrichum commune. This is selected as one of the largest and commonest of 
mosses. If any other genus is more readily obtainable, the teacher may as well use 
it. For an excellent account of the structure and physiology of mosses, consult 
Bennett and Murray’s Cryptogamic Botany. For the determination of species, see 
Lesquereux and James’ Mosses of North America. 
2 Fresh specimens are best, but dried ones will do nearly as well. 
