124 



MORPHOLOGY OP SPBRMATOPHYTES 



III. THE GAMETOPHYTES 



THE FEMALE GAMETOPHTTB 



While the female gametophyte conforms in a general way to 

 the Gymnosperm type, there are certain remarkable deviations 

 in Tumhoa and Gnetum which are suggestive of a possible 

 method of derivation of the embryo sac structures of Angio- 

 sperms. 



Fig. 89. — Ephedra : A, young ovule showing a row of three potential raegaspores ; £, 

 upper part of nuoellus after fertilization, showing the free cells of the proembryo 

 within.the two oospores, x 64; 0, suvspensors developing from the free cells, passing 

 from the oospore into the endosperm, and each bearing at tip an embryonal cell, 

 X 64; D-F, later stages in the development of the embryo, x 15i\ A, E. campy- 

 B-F, E. aUissima. — After Sthasbuhgek. 



Ephedra. — According to Strasburger's account ^ for E. cam- 

 pylopoda, the mother cells organize a row of three potential 

 megaspores, the lowest of which is the fertile one (Fig. 89, A). 

 In case several fertile megaspores begin to enlarge, one finally 

 dominates and develops the gametophyte. 



The details of the germination of the megaspore are lacking, 

 but Strasburger's outline is tlie usual one among Gj-mnosperms. 



