PTERIDOPHYTA 



291 



B 



Fig. 246. Development of the archegonium of Dryopteris, X350. A, division of arche- 

 gonium initial into an inner and outer cell, the latter having again divided anticlinally to 

 form two neck cells; B, formation of central cell and basal cell; C, division of central cell 

 into ventral cell and neck canal cell; D, division of neck canal cell nucleus; E, nearly mature 

 archegonium with egg, ventral canal cell, and binucleate neck canal cell; F, archegonium 

 with egg ready for fertilization. 



Summary. The Filicales are homosporous and leptosporangiate. 

 The sporangia are borne on the abaxial side of the leaves and are not in 

 synangia. The sporangium wall, one layer of cells thick, has an annulus. 

 The vernation is circinate. The gametophyte is flat, green, and thin 

 (sometimes filamentous); with few exceptions it is without an endophytic 



