CHAPTER XIV 



PHYLUM VIII. BRYOPHYTA 

 THE MOSSWORTS 



418. This phylum includes plants of much greater 

 complexity than any of the preceding. In very many 

 cases they have distinct stems and leaves, whose tissues 

 often show a differentiation into several varieties. In 

 the sexual organs the cell to be fertilized (the egg) is from 

 the first enclosed in a protective layer of cells, and after 

 fertilization it develops into a complex spore-bearing 

 body. 



419. The life-cycle of the Mossworts includes a dis- 

 tinct alternation of generations. The immediate prod- 

 uct of the fertilization of an egg is not a thalloid or leafy 

 plant like that which bears the sexual organs, but, on the 

 contrary, it is a many-celled leafless structure, spherical 

 or approximately cylindrical, which eventually produces 

 spores internally. The plant which produces the sexual 

 organs is the gametophyte, while that which produces the 

 spores is the sporophyte. 



420. So the Mossworts have a marked duality, and we 

 must consider both phases when we wish to get a complete 

 idea of any particular plant. This duality has permitted 

 the acquisition of the land habit, since the gametophytes 

 have retained some of their aquatic characteristics, while 

 the sporophytes have become modified for a terrestrial 

 life. Accordingly in Bryophytes we find the beginning of 

 the terrestrial habit in green plants. 



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