PTERIDOPHYTA 



275 



flat, green, and aerial. It is relatively thick and contains an endophytic 

 fungus. The development of the antheridium is like that of the Ophio- 

 glossales. The inner portion of the embryo forms the stem, leaf, and root, 



Fig. 231. Development of the archegonium of Angiopteris evecta, X350. A, division of 

 archegonium initial into primary neck cell and central cell; B, anticlinal division of primary 

 neck cell; C and D, periclinal division of central cell to form neck canal cell and ventral 

 cell; E, formation of two tiers of neck cells; F, division of ventral cell to form ventral canal 

 cell and egg; G and H, formation of a single binucleate neck canal cell, of three tiers of neck 

 cells, and of the sterile jacket; I, mature archegonium with egg ready for fertilization. 

 {After Haupt.) 



the outer portion the foot. The Marattiales have characters in common 

 both with the Ophioglossales and the Filicales and, in their degree of com- 

 plexity, occupy a position between them. These three orders do not form 

 a phylogenetic series. Instead, they seem to have been derived indepen- 

 dently from a common ancestry. 



