The individuality of the chromosomes and their serial arrangement, etc. 139 



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Explanation of Figures in Plates XI and XII. 



All the figures were drawn with the aid of a camera lucida, and with a Zeiss 

 apochromatic 3 mm. objective and compensating ocular 18. x 2400. 



Plate XI. 



Fig. 1. Cells in the plerome. Nuclei containing chromosomes with the serial 

 arrangement in evidence. 



Fig. 2. Cell in the wall of an ovule. Resting condition. 



Fig. 3. Tapetal cell. Early prophase. 



Fig. 4. Cells in the embryonic region of a root-tip: a and b are in the plerome; 

 c and d are in the region of the periblem and dermatogen ; e is in the calyptrogen. Chro- 

 mosomes are present in all of the nuclei. 



Fig. 5. Cells in the periblem: a during late telophase; i during early prophase. 

 Upper portion of nucleus h not in the section. 



Fig. 6. Cell in periblem during prophase; lower portion of nucleus not in the 

 section. 



Fig. 7. Cells in the filament of a stamen, a during prophase, 5 in resting stage. 



Fig. 8. Cell during mid-prophase. Spirem is wound about the nucleole. 



Fig. 9. Optical section through a nucleus in the same stage as shown in fig. 8. 

 In the sequence of division this stage follows the one shown in fig. 11. 



Figs. 10 and 11. Stages in prophase showing the discrete spirem and the early 

 appearance of spindle fibres. 



Fig. 12. Prophase after nuclear membrane has broken down. 



Fig. 13. Lateral view of an equatorial plate. 



Fig. 14. Polar view of an equatorial plate in the early stages of its development. 



Fig. 15. Cell in anaphase, lateral view. 



Fig. 16. Late anaphase showing rather heavy spindle and polar fibres. 



Fig. 17. Early telophase. Cell plate forming. 



Fig. 18. Telophase. Chromosomes separating out in series. 



Plate XII. 



Fig. 19. Nucleus of microspore mother-cell in the resting stage. Lower part of 

 nucleus not in the section. 



Fig. 20. Nucleus preparing for synapsis. Chromosomes are spinning out and 

 show attachments to nuclear membrane as at a and &. 



Fig. 21. Nucleus in a stage preceding synapsis. Chromosomes spun out into 

 a fine leptoneme which is attached to the nuclear membrane at several points. 



