134 



PLANT STEUCTUBES 



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 tlie apex of the 

 plant. This notcli is always 

 a conspicuous feature. 



The antheridia and arch- 

 egonia are usually developed 

 on the under surface of the 

 prothalliuni (Fig. Ill, A), 

 and differ from those of all 

 Bryophytes, except the ^i)t- 

 thiiceroK forms, in being sunk 

 in the tissue of the prothal- 

 lium and opening on the sur- 



FiG. 115. Development of yanietn])liyte 

 of PIcrh: the figure to tlie left shows 

 the old spore (5), the rhizoid {('), and 

 the thalhis (.1); that to the ri^'lit is 

 older, stiowini; the same parts, and 

 also the apical cell [D). — Caldwell. 



Fig. 116. Young gametophyte of Pteiis, 

 showing old spore wall (B1, rhizoids 

 (('\, apical cell {ID. a young anther- 

 idium (A'), and an older one in which 

 sperms liave organized i,F). — Cald- 

 well. 



