164 PLANT BIOLOGY 



entire fern. Each student should study a prothallus with a hand 

 magnifier, making an enlarged drawing of the same to show its 

 form and the position and shape of the rhizoids, antheridia, and arche- 

 gonia. A demonstration of the steps in the life history may well 

 be shown from charts. 



B. Mosses 



181. The moss plant. A second group of flowerless plants 

 includes the mosses. In general, mosses are smaller plants than the 

 ferns, but like them are usually found in damp, shady places. If 

 one examines a moss plant when it is " in fruit," a slender stem will 

 be seen projecting from the leafy part below. At the upper end 

 of this slender stem, a covered cup-like structure is evident (Fig. 

 84, A,k). This cup, or capsule as it is called, is filled with tiny dust- 

 like particles, which when examined with a compound microscope 

 prove to be cells. They are called spores. The spores are repro- 

 ductive bodies similar to those produced in the spore cases of ferns. 



182. The moss protonema. When these bodies are ripe, the 

 capsule opens and discharges some of the spores, which fall to the 

 ground and soon begin to grow, forming at first an elongated cell 

 (Fig. 84, H) which later divides, giving rise to two cells. This 

 process continues until a slender, green, thread-like mass is formed, 

 with many branches. This thread-like mass is called the protonema 

 (Fig. 84, G). Some of the branches produce buds which finally 

 grow into the leafy structure which we know as the moss plant 

 (Fig. 84, B, A). 



183. The sexual generation of the moss. - At the top of some 

 moss plants at certain seasons of the year, in the midst of the rosette 

 of green moss leaves, may be found tiny flask-shaped organs, the 

 archegonia (ovaries) (Fig. 84, F). At the base of each of these 

 organs is produced an egg-cell. Sometimes in the same moss plant, 

 and sometimes in another, are to be found club-shaped organs called 

 antheridia (spermaries) (Fig. 84, E). In the antheridia are pro- 

 duced sperm-cells (Fig. 84, D). At the proper time the sperm- 

 cells make their way into the archegonia, and when a sperm-cell 



