2S0 BOTAXICAL GAZETTE [april 



PLATE XIV 



Euphorbia Preslii. — Fig. i. — Appearance of a papilla which will develop 



into a cyathium. 



Fig. 2. — Staminate flowers and involucre developing at base of papilla. 



Fig. 3. — Ovules appearing at top of papilla, and carpels, staminate flowers, 

 and involucre at base; at the left, a secondary staminate flower. 



Fig. 4. — Longitudinal section of cyathium, showing 2 ovules within the 

 ovary, and developing staminate flowers at base of pistillate flower; integu- 

 ments have not yet appeared. 



Fig. 5. — Nucellus, containing megaspore mother cell, but with no integu- 

 ments as yet. 



Fig. 6.— Inner integument just appearing at base of nucellus. 



Fig. 7. — Inner and outer integuments at base of nucellus; embryo sac is 

 developing. 



Fig. 8. — Obturator appearing on placenta, and outer integument over- 

 topping inner. 



Fig. 9. — Obturator pushing up to nucellus. 



Fig. 10. — Mature embryo sac deeply imbedded in tissue of nucellus, which 

 has developed a beak; the long cells of obturator have filled space between 

 nucellus and placenta. 



Fig. 11. — Xucellus, showing megaspore mother cell. • , 



Fig. 12. — Megaspore mother cell before division. 



Fig. 13. — Axial row of 4 megaspores. 



Fig. 14. — Functional megaspore, now deeply imbedded in nucellar tissue. 



Fig. 15. — Binucleate embryo sac. 



Fig. 16. — Four-nucleate embryo sac. 



Fig. 17. — Four-nucleate embryo sac, with 2 of nuclei near center of sac; 

 an unusual condition. 



Fig. 18. — Mature embryo sac. 



Fig. 19. — Polar nuclei have moved nearer center of sac; synergids and 

 antipodal cells seem to have disintegrated. 



Fig. 20. — Two-celled embryo, with endosperm nuclei; one of latter 

 between embryo and micropylar end of sac. 



Fig. 21. — Four-celled embryo; several endosperm nuclei between embryo 

 and micropylar end of sac. 



Fig. 22. — Embryo a globular mass of cells. 



Fig. 23. — Still later stage in development of embryo. 



PLATE XV 



E. Preslii. — Fig. 24. — Longitudinal section of seed, with embryo at 

 micropylar end of embryo sac, and endosperm nuclei distributed in peripheral 

 region of sac. 



Fig. 25.— Elongated embryo imbedded in endosperm. 



Figs. 26, 28, 29, 30. — Elongation of embryo and appearance of cotyledons. 



