MOSSES 317 



or in the end of a short branch in some species. The sexual 

 organs are sperm and egg cases (antheridia and archegonia). 

 They are borne usually in different groups on the end of the 

 stem or a short branch, either on the same plant (moncecious, or 

 homothallic) or on different plants (dioecious, or heterothallic). 



Fig. 293. 

 Pigeon wheat mass (Polytrichum) in fruit. 



484. The hairy-cap moss (Polytrichum). The hairy-cap 

 moss, or as it is sometimes called the " pigeon wheat " moss, is 

 an excellent one for study because of its common occurrence 

 and wide distribution, its large size, and the striking difference 

 between the male and female plants. It grows usually in mod- 

 erately moist situations or in swampy ground. The plants form 

 dense tufts or an extensive turf, the male and female plants 

 usually grouped by themselves. The leaves are quite narrowly 

 pointed and rather rigid. The male plants are shorter than the 

 female plants, and at the end of the stem the leaves are crowded 

 into a spreading rosette, in the center of which the sperm cases 

 are crowded. In the female plants the terminal leaves are rather 



