CHAPTER VII 

 THE PTERIDOPHYTA-FILICINE^-OPHIOGLOSSACE^ 



In tracing the evolution of the Bryophytes from the lowest to 

 the highest types the gradual increase in the importance of the 

 second generation, the sporophyte, is very manifest. This may 

 or may not be accompanied by a corresponding development of 

 the gametophyte. In the line of development represented by 

 the higher Mosses, in a general way the two have been parallel, 

 and the most highly differentiated gametophyte bears the most 

 complicated sporophyte, as may be seen in Polytrichum, for 

 example; but in the Hepaticae this is not the case, and among 

 the Anthocerotes much the most highly organised sporophyte, 

 that of Anthoceros, is produced by a very simple gametophyte. 



In this evolution of the sporophyte, it approaches a condition 

 where it is self-supporting, but in no case does it become abso- 

 lutely so. A special assimilative tissue, it is true, is developed, 

 and in some of the true Mosses, such as Splachnum, this goes so 

 far that a special organ, the apophysis, is formed; but, as we 

 have seen, the sporogonium is dependent for its supply of water 

 and nitrogenous food upon the gametophyte, with which it 

 remains intimately associated, and upon which it lives as a 

 parasite. 



The type of structure found in the gametophyte of the 

 Muscinese seems to be imperfectly fitted for a strictly terres- 

 trial life. The gametophyte of all Archegoniates is more or less 

 amphibious. Free water is essential for the act of fecundation, 

 and the gametophyte seems never to have solved satisfactorily 

 the problem of an adequate water supply, except by returning 



to the aquatic condition. 



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