134 



PLANT STEUCTUEES 



being a conspicuous object in connection with the spore- 

 phyte. 



At the bottom of the conspicuous notch in the prothal- 

 Hum is the growing point, 

 representing the apex of the 

 plant. This notch is always 

 a conspicuous feature. 



The antheridia and arch- 

 egonia are usually developed 

 on the under surface of the 

 prothallium (Fig. Ill, A), 

 and differ from those of all 

 Bryophytes, except the An- 

 thoceros forms, in being sunk 

 in the tissue of the prothal- _ 

 lium and opening on the sur- ^ 



Fig. 115. Development of gametophyte 

 of Pteris: the figure to the left shows 

 the old spore {B), the rhizoid (C), and 

 the thallns (.4); that to the right is 

 older, showing the same parts, and 

 also the apical cell (Z>).— Caldwell. 



Fig. 116. Young gametophyte of Pteris, 

 showing old spore wall {B), rhizoids 

 (C), apical cell (/)), a young anther- 

 idium {E), and an older one in which 

 sperms have organized (i?').— Cald- 

 well. 



