I 



1907] LAND— EPHEDRA TRIFURCA 



291 



Stalk -cell nucleus; /, tube nucleus; pt, pollen tube; 0, egg nucleus; v, ventral 

 nucleus; p, proembryonal nucleus; st, suspensor tube; sn^ suspensor nucleus; 

 en, embryo -initial nucleus; s, suspensor; e^ embiy^o -initial cell. 



PLATE XX 



500 



poll 



are the tw'o male nuclei lying side by side, above and to the right is the stalk 

 nucleus. X500. 



solution. X500. 



gth 



Median lonedtudinal section throueh an archeeonium 



pollen tubcj the fusion of a male nu 

 and the second male nucleus. X250. 



fragments 



• > 



afnitotically, 



X2S0. 



PLA TE XXI 



Fig. 6. Upper end of egg, showing second male nucleus^ small cells derived 

 from various sources, and one of two functioning proembryos. X500. 



Fig. 7. Upper end of egg showing a stage of the second male nucleus slightly 

 later than in jig, 6^ the small ephemeral cells, and t^^o of four functioning pro- 

 embryos. X500. 



Fig. 8. Proembryos, showing incomplete cleavage of the cytoplasm. X500. 



Fig. 9. Three of five functioning proembr}'os; jacket nuclei in the egg cyto- 

 plasm; free masses of cytoplasm; also masses of cytoplasm remaining after the 

 proembryonal cells have been carved out. X500. 



Fig. 10. Disintegration of jacket cells. X500. 



Fig. II. One of the proembryos before formation of the suspensor tube; the 

 nucleus will shortly divide. X500, 



Fig. 12. Proembrj'o with two free nuclei and two papillae, the larger of which 

 is the beginning of the suspensor tube. X500. 



Fig. 13. Proembrj'o with suspensor tube; the larger nucleus is the embryo- 

 initial nucleus; the smaller will be the suspensor nucleus. X500. 



PLATE XXII 



Fig, 14. Cleavage plane cutting off the embr}'o -initial cell from the tip of the 

 suspensor tube. X500. 



Fig. 15. Detail of the cleavage plane separating the embryo initial from the 

 suspensor. X1900. 

 , Fig. 16. A stage slightly later than fig. 14. Xsoo. 



Fig. 17. Elongated suspensor with embr)^o -initial cell shortly before dividing. 



X500. 



