64 FOUNDATIONS OF BIOLOGY 



It is among the so-called VASCULAR PLANTS the Ferns 

 and Flowering Plants that the most highly specialized 

 plant body occurs. As will be explained in more detail later, 

 these plants exhibit in their life history an alternation of 

 generations: a sexual plant (GAMETOPHYTE) bearing gametes 

 gives rise to a non-sexual spore-bearing plant (SPOROPHYTE) 



Fia. 25. Gulfweed (Sargassum) showing the 'stem,' 'leaves,' and 

 the berry-like floats of the thallus. (From Coulter, Barnes, and 

 Cowles.) 



which hi turn produces a gametophyte. These two genera- 

 tions exhibit marked differences in structure. The game- 

 tophyte body is relatively very simple, consisting merely 

 of a few cells, the main function of which is to develop male 

 and female gametes. On the other hand, the sporophyte is 

 composed of a number of specialized tissues and organs, and 

 is the conspicuous generation which is recognized by everyone 

 as a 'Fern' or a 'Flowering Plant.' 



