134 



PLANT STRUCTURES 



being a conspicuous object in connection with the sporo- 

 phyte. 



At the bottom of the conspicuous notch in the prothal- 

 lium 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, .1), 

 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 gametophytc 

 of Pteris: the figure to the left shows 

 the old spore (B), the rhizoid ( O, and 

 the thallus U); that to the right is 

 older, showing the same parts, and 

 also the apical cell (D). CALDWELL. 



FIG. 116. Young gametophytc of Pteris, 

 showing old spore wall (B), rhizoid* 

 (Ct). apical cell (D). a young author 

 idium (K), and an older one in which 

 sperms have organized (F). 

 WELL. 



