CHAPTER VIII 



THE PTERIDOPHYTA OPHIOGLOSSACEyE 



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 develop- 

 ment 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 much the most highly organised sporophyte 

 here, that of Anthoceros, is produced by a very simple game- 

 tophyte. 



In this evolution of the sporophyte, it approaches a condition 

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

 absolutely 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. 



In the Pteridophytes the case is different ; here by the 

 development of a special organ, the root, the young sporophyte 

 is brought into direct communication with the source of supply 

 of water, and the food materials dissolved in it. In the few 

 cases where true roots are absent their place is taken by other 

 structures that perform their functions. The assimilative activity 

 is restricted to special organs, the leaves, except in a few cases 



