XXI] SPORANGIA 131 



over the distal end. and leads downwards to the stalk on the opposite side 

 of the sporangium. The line of dehiscence, defined structurally by narrow 

 thin-walled cells, gapes widely at ripeness (Fig. 421). This requires elbow- 



Fig. 420. /, Osmunda regalis, part of a meta- 

 morphosed sporophyll with aborted sporangia 

 attached superficially. //, Todea pcllucida, 

 part of a pinnule with sporangial stalks. 

 ///, transverse section of a fertile pinnule 

 of Osmunda, showing normal insertion of 

 sporangia. (All after von Goebel.) 



Fig. 421. Todca harhara Moore, 

 sporangium. A, in side view, 

 closed; B, seen from behind; 

 C, from in front, in both cases 

 after dehiscence : the annulus is 

 darkly shaded. ( x 80.) (After 

 Luerssen.) 



room, which the lax arrangement of the sporangia readily allows. The 

 spore-output is large, ranging in the famil)- from t}-pical numbers of 128 

 to 512. 



9—2 



