CHAPTER X 



FERNS 



106. Summary. Before studying the ferns, it is well to 

 note the progress that has been made by* the plants previ- 

 ously considered. It has been said that the Alga? and 

 Fungi together form the first great division of the plant 

 kingdom, the Thallophytes. The liverworts and mosses 

 together form the second great division, called the Bryo- 

 phytes, a name meaning "moss plants. " The ferns intro- 

 duce the third great division, called the Pteridophytes, which 

 means "fern plants." A summary of the contributions 

 made by the Bryophytes to the progress of plants is as 

 follows: 



(1) The land habit. The Bryophytes establish green 

 plants upon the land, and as a consequence begin to develop 

 those structures that the new conditions demand. 



(2) Alternation of generations. A life-history consisting 

 of alternating sexual (gametophyte) and sexless (sporo- 

 phyte) generations is finally established, although it is in- 

 dicated in the life-histories of certain Thallophytes. 



(3) Gametophyte the chlorophyll generation. In the alter- 

 nation the gametophyte generation develops the chloro- 

 plasts for food manufacture, and on this account is the con- 

 spicuous generation. When a moss or a liverwort is spoken 

 of, therefore, the gametophyte is usually referred to. 



(4) Sporophyte dependent. The sporophyte in the Bry- 

 ophytes is dependent upon the gametophyte for food, and 

 hence remains attached to it. Only by the Anthoceros forms 

 has a partial independence of the sporophyte been attained. 



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