FIG. 239. At the left is the "interrupted fern," or Clayton's fern (Osmunda 

 Claytoniana), in which sporangium-bearing leaflets (sp) are distinct and inter- 

 mediate with foliage leaflets. At the right is the royal fern (Osmunda regalis) 



A, a leaf with sporangium-bearing leaflets at its tip. B, (7, D, stages in the devel- 

 opment of sporangium-bearing leaflets from foliage leaflets. Both about one 

 third natural size 



287 



