CRYPTOGAMS 249 



power, the sperms will be seen swimming about in the 

 water. 



Make drawings of all structures seen. 



Reproduction in Mosses. Mosses admirably illustrate 

 the phenomena of alternation of generations. 



The life history of a moss plant may be described as fol- 

 lows : 1 . Spores are produced in the capsule of the plant 

 studied in the preceding exercise. The capsule, together 

 with its stalk (seta) is known as a sporophyte (spore plant). 

 Spores falling upon favorable soil germinate, forming a 

 delicate green plant called a protonema, which is made up of 

 numerous branching filaments. 



2. The protonemata have numerous hairlike structures 

 resembling root hairs, which are called rhizoids. They also 

 bear tiny buds which ultimately develop into leafy moss 

 plants. 



3. The leafy moss plant is known as a gametophyte, because 

 it bears the sex organs, or gametes, carefully tucked away 

 among the minute leaves forming the rosette at its top. 



The male gamete is called an antheridium. The female 

 gamete is called an archegonium. 



The sexes may be on the same plant (monoecious) or upon 

 different plants (dioecious) as among flowering plants. 



Within the archegonia are egg cells and within the an- 

 theridia are numerous sperms. Fertilization is effected by 

 union of a sperm with an egg cell, whereupon the latter pro- 

 ceeds to develop into the spore-bearing plant (sporophyte), 

 thus making the life cycle complete. The sporophyte re- 

 mains attached to the leafy moss plant and grows upon it 

 like a parasite. Thus we have two alternating generations; 

 namely, the gametophyte which produces the eggs and 

 sperms, and the sporophyte, producing non-sexual spores. 



