458 Gregory . — Spore- Formation in Leptosporangiate Ferns. 
Fig. 5. Davallia Capensis. Longitudinal fission and contraction of the spireme, x 1000. 
Figs. 6, 7, 8, and 9, show later stages in the formation of the loops. The twisting of the limbs 
upon one another is shown in Figs. 8 to 10. 
Fig. 6. Onoclea sensibilis. x 1500. 
Fig. 7. Asplenium marinum. x 1500. 
Fig. 8. Scolopendrium vulgar e x Asplenium Ceterach. x 1500. 
Fig. 9. Asplenium Ceterach . x 1500. 
Fig. 10. Onoclea sensibilis. The longitudinal fission is rather less evident than in the earlier 
stages, x 1500. 
Fig. 11. Onoclea sensibilis. Showing the looped spireme. (Some of the loops are omitted for 
the sake of clearness. The chromatin granules are represented somewhat diagrammatically.) x 1000. 
Fig. 12. Asplenium marinum. The limbs of the loops are closely approximated to one 
another. x 1500. 
Fig. 12 a. Two of the loops ( a and b of Fig. 12) indicating the original longitudinal fission. 
x 2250. 
Fig. 13. Fadyenia prolifera. A late stage in which the longitudinal fission is clearly visible 
in the cut ends of the thread, x 1000. 
Fig. 130. From another nucleus of the same sporangium, showing the longitudinal fission 
of the spireme, x 2250. 
Fig. 14. Fadyenia prolifera. The spireme shortly before segmentation into the chromosomes 
takes place, x 1 500. 
Fig. 15. Onoclea sensibilis. The segmentation of the spireme into chromosomes. In some 
instances there are clear indications of the double nature of each limb, x iooo. 
Fig. 16. Scolopendrium vulgare x Asplenium Ceterach. Later stage, showing the various 
forms assumed by the chromosomes in the heterotype division, x 1000. 
Fig. 17. Chromosomes from the same nucleus, x 2250. 
Fig. 18. Asplenium marinum. Chromosomes of the heterotype division, x 2250. 
Fig. 19. Onoclea sensibilis. As Fig. 16. 
Figs. 20, 21. Onoclea sensibilis . Chromosomes of the heterotype division. The longitudinal 
fission may be indicated in surface view (Fig. 20) or through the bifid ends of the limbs of the 
chromosomes (Fig. 2 t). x 2250. 
Fig. 22, 23. Davallia capense. Two stages in the breaking down of the nuclear wall and 
the development of the spindle. There are indications of the original longitudinal fission in the 
limbs of some of the chromosomes. Fig. 22, x 1000; Fig. 23, x 2250. 
Fig. 24. Davallia capense. Formation of the spindle and movement of the chromosomes 
towards the equatorial plate. The limbs of the chromosomes are already slightly drawn apart, and 
their longitudinal fission is clear, x 1000. 
Fig. 24 a. Part of the same . x 2250. 
Fig. 25. Asplenium marinum. Metaphase of the heterotype division, x 1500. 
Fig. 26. The same. The section is tangential to the spindle and shows the chromosomes in 
face view, x 2250. 
Fig. 2 6 a. The same stage in Onoclea sensibilis. The chromosomes seen in profile, x 2250. 
Fig. 27. Asplenium marinum. Tangential section of the nucleus in anaphase of the heterotype 
division, x 1500. 
Fig. 28. Scolopendrium vulgare x Asplenium Ceterach. Late anaphase, x 1000. 
Fig. 29. Onoclea sensibilis. Telophase. Formation of a nuclear wall, x 1000. 
Fig. 30. From the same sporangium, showing a slightly later stage in which the nuclei have 
entered upon the homotype division, x 1000. 
Fig. 31. Onoclea sensibilis. Telophase of the homotype division, x 1500. 
Figs. 32, 33, and 34. Scolopendrium vulgare x Asplenium Ceterach. Three stages in the 
development of the spore. All x 1 500. 
