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BOTANY 



Adult Moss Plants. — It soon develops rhizoids; tiny buds appear that 

 in time form the adult moss plant. These adult plants may grow only 

 leaves, and become what are known as sterile plants; or they may develop 

 into a plant that bears at the summit the little rosette of leaves previously 

 referred to. Within the rosette lie a number of tiny organs which resemble 

 the antheridia of the ferns in structure. They are in fact antheridia and 

 hold large numbers of sperm cells. Other moss plants bear at the summit 

 of the stem a tuft of leaves which hide a number of small flask-shaped 

 archegonia. The archegonia contain each a single egg cell. These plants 



form the sexual generation of the moss. After 

 a sperm cell has been transferred to the egg 

 cell a fusion of the two cells takes place. 

 This, we remember, is the process of fertili- 

 zation. In the mosses as well as the ferns 

 the fertilization of the egg cell results in the 

 growth of that part of the plant which forms 

 and bears the asexual spores. 



Alternation of Generations. — In the 



mosses also we have an alternation 

 of generations. The leafy moss, bear- 

 ing among its leaves the sex organs, 

 antheridia and archegonia, gives place 

 to a stalk and capsule bearing the 

 asexual spores. This spore-bearing 

 portion of the plant does not appear 

 until after fertilization; then it grows 

 directly out of that part of the plant 

 that produces the egg cell. In fact, 

 if we make a microscopic examination 

 of this archegonium directly after fer- 

 tilization, we find that the sporo- 

 phyte is a direct outgrowth from the 

 fertilized egg cell. 



Sporophyte a Parasite. — One interest- 

 ing fact comes out in connection with 

 this growth of the sporophyte. It has 

 no green leaves and must therefore obtain all its nourishment from 

 the leafy moss plant, or gametophyte. The spore-bearing part of 

 the plant is thus actually a parasite upon the gametophyte. 



Pigeon wheat. A moss showing 

 egg-bearing gametophyte and 

 sporophyte (stalk and capsule), 

 the latter entirely dependent 

 upon the former. 



