CHAPTER LXI 

 ALTERNATION OF GENERATIONS 



373. Life history of a moss. In the moss plants, the individuals that 

 we ordinarily have in mind when we speak of moss bear at the end of 

 a leafy stem a group of sexual organs. Some individuals carry egg- 

 producing organs ; others bear sperm-producing organs (see Fig. 1 48). 



FIG. 148. Reproduction in moss 



a, a leafy moss plant (Hypnum molluscum) ; b, section cut lengthwise through tip of one 



of the branches, showing position of archegonia, or egg-bearing organs ; c, single arche- 



gonium, more highly magnified, showing single large egg cell ; d, enlarged view of 



antheridium, or sperm-bearing organ, of Polytrichttm formosum, discharging sperm cells ; 



, greatly magnified view of sperm cells ; _/", tip of leafy plant from the archegonium of 



which a spore plant has grown, showing stalk and spore capsule 



320 



