REPRODUCTION IN PLANTS 



101 



of our flora, since they form heavy growths or carpets of vege- 

 tation which hold back much of the rainfall so that it sinks 

 into the soil. Although there are over 8000 species which 

 botanists include in the order Bryales of the Phylum BRYO- 



Fia. 53. The life history of a Moss, chiefly Polytrichum. a, the entire plant 

 (gametophyte and sporophyte), X }. b, median vertical section of the capsule in 

 which spores are formed, X 6, with spore (c) and germinating spore (d), X 300; e, 

 spore germinated to a protonema with a bud which forms leafy plant (gametophyte), 

 X 75; /, tip of gametophyte with two archegonia, X 2; g, archegonium in section 

 showing egg, X 16; h, tip of gametophyte with antheridia, X 2; t, antheridium, X 1C; 

 j, a single liberated sperm, X 600; k, gametophyte with sporophyte developing in 

 enlarged and transformed archegonium. (After Ganong, Dodel-Port and others.) 



PHYTA, a general description of a typical common Moss, such 

 as Polytrichum communae, will suffice for the purpose at 

 hand. (Fig. 53.) 

 The shoot of a moss plant is differentiated into stem and 



