2 I I 
certain Varietal and Hybrid Ferns. 
Fig. 2. Three adjacent spore mother-cells whose nuclei show successive stages in the withdrawal 
of the network from the nuclear periphery ; the first indication of the preparation for ‘ synapsis 
x 2250. 
Fig. 3. The chromosomes are coming out of second contraction. Note the bipolar spindle, and 
the massing of the chromosomes at the two parts of the nuclear periphery which will be invaded by 
the fibres, x 2250. 
Fig. 4. Polar view of a heterotype equatorial plate. x 2250. 
Fig. 5. Heterotype equatorial plate, x 2250. 
big. 6. Polypodium vulgare. Archesporial nucleus in prophase showing the premeiotic spindle 
origin. One of the spindle cones is distinctly bilobed. Note the granules towards which many of 
the fibres converge, x 2250. 
Fig. 7. Fully formed chromosomes. The four spindle cones are in the same plane, x 2250. 
Fig. 8. The fibres have invaded the nucleus, and the chromosomes are becoming arranged on 
the spindle. Two of the spindle cones have come together, the other two are still wide apart. 
X 2250. 
Fig. 9. Slightly later stage in which the quadripolar spindle has become decidedly bipolar, 
x 2250. 
Fig. 10. Polar view of a heterotype equatorial plate, x 2250. 
Fig. 11. Aberrant mitosis, the result of an incomplete first meiotic division. The narrow 
bridge joins the two sac-like nuclear extremities. The interzonal spindle fibres are clearly to be seen, 
x 2250. 
PLATE XVII. 
Fig. 12. Polypodium vulgare (continued). Telophase of the first meiotic division showing the 
extrusion of ‘ chromatic droplets some of which are still joined to the nuclear chromatin by con¬ 
spicuous threads, x 2250. 
Fig. 13. Nucleus of tetrad after the second meiotic division. Exlranuclear ‘ chromatin droplets ’ 
are in direct connexion with the nuclear threadwork. x 2250. 
Fig. 14. Polypodiu 77 i vulgare var. elegantissimum (‘reverted’). Nucleus of tetrad showing 
‘ chromatin droplets ’ still attached, x 2250. 
Fig. 15. Nucleus going into synapsis. A stage slightly later than Fig. 2. x 2250. 
Fig. 16. Nucleus having passed through the ‘hollow spireme’ stage is passing into second 
contraction. There is a marked massing of the spireme at the areas where the spindle radiations are 
in contact with the nucleus, x 2250. 
Fig. 17. A later stage showing the increased massing of the chromatin, x 2250. 
Fig. 18. Heterotype diaster. The chromosomes pass to the poles in an irregular manner, 
x 2250. 
Fig. 19. Polypodium vulgare var. elegantissimum (from varietal leaf). Polar view of a hetero¬ 
type equatorial plate, x 2250. 
Fig. 20. Aberrant form of the first meiotic division, giving off droplets of chromatin. The cell- 
plate is incomplete, x 2250. 
Fig. 21. Aberrant nuclei of the second meiotic division. These nuclei will break apart as the 
tetrads mature, x 2250. 
Fig. 22. Polypodium Schneideri. General view of a sporangium with its spore mother-cells. 
Note the scanty tapetum. x 498. 
PLATE XVIII. 
Figs. 23 and 24. Polypodium Schneideri (continued). An abortive sporangium dying back to 
the placenta (two drawings of the same sporangium in consecutive planes), x 498. 
Fig. 25. Nucleus passing into synapsis. A stage between Figs. 2 and 15. x 2250. 
Fig. 26. Nucleus coming out of the ‘hollow spireme’ and beginning to prepare for the second 
contraction. There is a slight concentration of the spireme towards the spindle fibres, x 2250. 
Fig. 27. Chromosomes coming out of second contraction. The spindle fibres are feebly 
developed as compared to those of P. vulgare and to the variety elegantisshnum at the corresponding 
stage, x 2250. 
P 2 
