in Li Hum Martagon : II. Spermatogenesis . 223 
chromatin-granules : n, nucleolus, round which some of the chromosomes are still 
clustered, x 585. 
Fig. 9 a. Single immature chromosome from nucleus about same age as that of 
Fig. 9, more highly magnified. 
Fig. 10. Pollen-mother-cell from thick serial section (15 A 1 ). The chromosomes 
are nearly mature : n, n, fragments of nucleolus, x 585. 
Fig. 10 a. Pollen-mother-cell from serial section (10 ^ thick). The spindle is 
just appearing ; part of the nuclear membrane is still seen at x . Small drops, 
probably of nucleolar matter, are visible in the cytoplasm, x 585. 
Fig. 11. Pollen-mother-cell from same section as Fig. 10. The asymmetrical 
spindle is just formed, x 585. 
Fig. 11 a. Pollen-mother-cell from thick serial section (12-5 a<). The spindle 
is still asymmetrical, and though the chromosomes are attached to the spindle- 
fibres, they are not as yet arranged in an equatorial plate, x 585. 
Fig. 12. Pollen-mother-cell from thin serial section (7-5 p). Part of the nuclear 
plate is seen tangentially, x 585. 
Fig. 13. Pollen-mother-cell from thin serial section (10 f). Four chromosomes 
are seen just before the separation of their segments is complete, x 585. 
Fig. 14. Pollen-mother-cell from same preparation as Fig. 12. The daughter- 
chromosomes are formed and on their way to the poles. Each is V-shaped, with 
the angle more or less bent back, x 585. 
Fig. 15. Pollen-mother-cell from same anther as Figs. 12 and 14. Two 
daughter-nuclei are formed with cell-plate between them. X585. 
Figs. 16-22. Second karyokinesis in pollen-mother-cell. 
Fig. 16. Tangential view of daughter-nucleus in spirem-stage. x 1000. 
Fig. 17. Similar view of rather older nucleus. The coils are being pulled out in 
the direction of the future spindle, x 1000. 
Fig. 18. Nine chromosomes formed from the spirem-daughter-nucleus. Nos. 1, 
2, 3> 4> 5, and 9 are V-shaped, x 1000. 
Fig. 19. Five chromosomes on spindle of daughter-nucleus. All show V-shape. 
x 1000. 
Fig. 21. Two chromosomes from nuclear plate of daughter-nucleus just as 
segments are separating, x 1000. 
PLATE XI. 
Fig. 20. Pollen-mother-cell divided into two compartments, each containing 
a nuclear plate. X 585. 
Fig. 22. Pollen-mother-cell divided : the nucleus of each daughter-cell has 
formed a diaster, x 585. 
F igs. 23-28. Karyokinesis of pollen-grain-nucleus. 
Fig. 23. Sections of immature pollen-grain, (a) parallel to long axis, (b) per- 
pendicular to long axis, n, nucleus, x 300. 
Fig. 24. Section of pollen-grain with nucleus in which the spirem-ribbon is 
formed. A differentiated mass of cytoplasm is seen near the nucleus, x 585. 
Fig. 25. Tangential view of nucleus in spirem-stage : n , nucleolus, xiooo. 
Fig. 26. Five chromosomes arranged on spindle. Longitudinal fission not yet 
apparent. xiooo. 
