154 PLANT STRUCTURES 



lowest plants the gametophyte is represented by the whole 

 plant structure. When the sporophyte first appears it is 

 dependent upon the gametophyte (some Thallophytes and 

 the Bry ophytes), and is relatively inconspicuous. Later 

 the sporophyte becomes independent (most Pteridophytes), 

 the gametophyte being relatively inconspicuous. Finally 

 (heterosporous Pteridophytes) the gametophyte becomes 

 dependent upon the sporophyte, and in Spermatophytes is 

 so inconspicuous and concealed that it is only observed by 

 means of laboratory appliances, while the sporophyte is the 

 whole plant of ordinary observation. 



