Welsford. — The Genesis of the Male Nice lei in Lilium. 269 
Fig. 4. Lilium auratum. The tube and generative nuclei lying close together and showing no 
differentiation, x 800. 
Fig. 5. Lilium auratum. The tube nucleus has moved towards the centre of the cell; its 
membrane is not yet clearly defined. The formation of the generative cell has begun, x 800. 
Fig. 6. Lilium auratum. Young generative cell, showing a row of granules. The cell 
membrane is not yet complete and the cell is delimited by vacuoles, x 1,200. 
Fig. 7. Lilium auratum. Young generative cell, showing the differentiation of cytoplasm and 
the extrusion of granules from the nucleus, x 1,200. 
Fig. 8. Lilium auratum. Longitudinal section of a pollen-grain, showing the faintly stained tube 
nucleus and the more deeply stained generative nucleus lying in the generative cell, x 800. 
Fig. 9. Lilium auratum. Transverse section of generative cell, showing one of the polar 
granules. Delicate cross-connexions can be seen between the threads of the spireme, x 1,200. 
Fig. 10. Lilium auratum. A generative pollen-grain, showing the tube nucleus and generative 
cell being carried in a stream of protoplasm towards the tube, x 500. 
Fig. 11. Lilium Martagon. Generative cell in pollen tube. The nucleus has already begun to 
enlarge preparatory to division. The two polar granules are shown, x 800. 
Fig. 12. Lilium Martagon. Later stage, showing the longitudinally split thread. The genera- 
tive cell is clearly shown, x 800. 
Fig. 13. Lilium Martagon. Later stage; the spireme still shows the split in places. The 
cytoplasm of the generative cell stains very faintly. The curved shape of the spireme is indicated, 
x 1,200. 
Fig. 14. Lilium Martagon. About the same stage as Fig. 13. x 1,200. 
Fig. 15. Lilium Martagon. Shows the twelve split chromosomes lying in the generative cell. 
x 1,200. 
Fig. 16. Lilium Martagon. Shows the twelve split chromosomes lying in the generative cell, 
x 1,200. 
Fig. 17. Lilium Martagon. Ditto, x 800. 
Fig. 18. Lilium Martagon. Chromosome 7 from Fig. 17. x 1,800. 
PLATE XVII. 
Fig. 19. Lilium Martagon. Metaphase in generative cell; one of the polar granules is shown, 
x 800. 
Fig. 20. Lilium Martagon. Anaphase. The two groups of chromosomes are lying in the male 
cells, x 800. 
Fig. 21. Lilium Martagon. A later stage, x 800. 
Fig. 22. Lilium Martagon. The chromosomes have joined up. The generative cytoplasm is 
very thin and spread out. X 1,200. 
Fig. 23. Lilium Martagon. A rather later stage; the spireme thread is thickening and the 
whole nucleus is beginning to show a curvature, x 1,200. 
Fig. 24. Lilium Martagon. Two male nuclei at a slightly later stage than that shown in 
Fig. 23. One of the nuclei has moved away from its cytoplasm. Both masses of cytoplasm show 
a more or less band-like group of granules. These nuclei are about 8 mm. from the top of the 
ovary, x 800. 
Fig. 25. Lilium Martagon. A rather older male nucleus, showing its curved, almost spiral 
shape. The protoplasm has a disturbed appearance. This nucleus is also about 8 mm. from the 
top of the ovary, x 1,800. 
Fig. 26. Lilium auratum. Part of a pollen tube dissected from the base of the style. The 
two male cells are clearly seen, each with its curved nucleus and numerous granules. The tube 
nucleus is also shown, x 500. 
Fig. 27. Lilium atiratum. Two male cells in a bent-over pollen tube about two mm. from 
the apex of the stigma, x 1,200. 
Fig. 28. Lilium Martagon. Two male cells in the tube ; one of the nuclei has almost parted 
from its cytoplasm, x 800. 
Fig. 29. Lilium Martagon. A male nucleus and its faintly stained cytoplasm lying in the 
pollen tube, x 800. 
Fig. 30. Lilium auratum. A pollen tube from the base of the style, showing the thickened 
tip, the lobed tube nucleus, and one of the male cells. X 500. 
