J- /.A. VIVO NTS AND SEED-PLANTS. 



61 



"cushion," as it is called, are produced the sexual organs. 

 (See further under Reproduction, Tart III.) 



70. Reduction of gametophyte. — In a few of the fernworts 

 the gametophyte is filamentous, or tuberous, and more or less 



N 



Fig. 75. — Sporophyte of a fern, Polypodiu 

 stem, hearing seenndary roots and 



ilgare, showing horizontal underground 

 ■s. Natural size. — From Bessey. 



completely subterranean and colorless. Such prothallia derive 

 tluir food from decaying plant-offal. 



In higher plants of this group the gametophyte becomes 

 still further reduced in size and structurally simplified, until 

 in some species it is hardly more than a few cells surrounding 

 the sexual organs. These reduced forms grow by the use of 



