1902] A MORPHOLOGICAL STUDY OF THUJA 259 



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Fig. I. Pollen grain shortly after separation of tetrad. 



Fig. 2. Pollen grain showing tube nucleus and generative cell. 



Fig. 3. Pollen tube with tube and stalk nuclei in advance of the body 



cell. 



Fig. 4. Pollen tube entering nucellus. 



Fig. 5. Body cell preparing to divide. 



Fig. 6. Tip of pollen tube with two male cells and tube and stalk nuclei. 



Fig. 7. Male cells at the bottom of an archegonium which failed to 



function. 



Fig. 8. Longitudinal section through upper end of prothallium. showing 

 archegonium initials. 



Fig. 9. Archegonium complex after neck cells have been cut oS. 



Fig. 10. Archegonium complex just before cutting off the ventral 

 nucleus; jacket cells very active, neck cells disintegrating, and body cell 

 preparing to divide. 



Fig. 1 1. Transverse section through middle of an archegonium complex, 

 showing the large vacuoles. 



Fig. 12. Cutting off the ventral nucleus. 



Fig. 13. Probable division of the ventral nucleus. 



Fig. 14. Male cell entering the ^g,g. 



Fig. 15. Male nucleus after slipping out of its cytoplasmic sheath. 



Fig. 16. Male and female nuclei in contact. 



Fig. 17. Division of ventral nucleus in upper end of oospore ; only three 

 of the four nuclei shown ; below is the proembryo, with the suspensors begin- 

 ning to elongate 



Fig. 18. Division of the fusion nucleus. 



Fig. 19. The two nuclei resulting from the division of the fusion nucleus; 



the ventral nucleus is above. 



Fig. 20. The two nuclei at the bottom of the egg. 



Fig. 21. Second division of the proembryo. 



Fig. 22. Four nuclei resulting from the second division ; the ventral 



-nucleus above. 



Fig. 23. Third division of the proembryo; this figure shows the last 



simultaneous division of the nuclei. 



Fig. 24. Upper tier of nuclei dividing to form suspensors. 

 ■ Fig. 25. Second tier elongating into suspensors. 



Fig. 26. Suspensors, with embryo. 



Fig, 27. The most advanced one of a number of embryos growing 

 upward through the nucellus ; in the preparation from which the figure is 

 drawn there are the usual number of embryos growing downward. 



Fig. 28. Transverse section of an embryo, showing bipartite appearance. 



