280 Reed . — The Nature of the Double Spireme in Allium Cepa. 
10. Lawson, A. A. : Nuclear Osmosis as a Factor in Mitosis. Trans. Roy. Soc. Edin., vol. xlviii, 
P- r 37- 
11. : The Phase of the Nucleus known as Synapsis. Trans. Roy. Soc. Edin., 
vol. xlvii, p. 591. 
12. : A Study in Chromosome Reduction. Trans. Roy. Soc. Edin., vol. xlviii. 
13. Leitgeb, H. : Krystalloide in Zellenkernen. Mitt, aus dem Bot. Inst, zu Graz, Jena, p. 115. 
14. LundigArd, H. : Ueber Kerntheilung in den Wurzelspitzen von Allium . Svensk Botanisk 
Tidskrift, Bd. iv, p. 188. 
15. Merriman, M. C. : Vegetative Cell-division in Allium. Bot. Gaz., vol. xxxvii, p. 178. 
16. Muller, H. A. C. : Ueber karyokinetische Bilder in der Wurzelspitze von Yucca. Pringsh. 
Jahrb. f. wiss. Bot., Bd. xlvii, p. 99. 
17. : Kemstudien an Pflanzen. Archiv f. Zellforschung, Bd. viii. 
18. Nemec, B. : Ueber die karyokinetische Kerntheilung in der Wurzelspitze von Allium Cepa. 
Pringsh. Jahrb. f. wiss. Bot., Bd. xxxiii. 
19. Overton, J. B. : On the Organization of the Nuclei in the Pollen Mother-cells of Certain 
Plants. Ann. Bot,, vol. xxiii, p. 19. 
20. Schaffner, J. H. : Karyokinesis in Root Tips of Allium Cepa. Bot. Gaz., vol. xxvi, p. 225. 
21. Stomps, T. J. : Kerndeeling en synapsis bij Spinacia oleracea. Amsterdam, 1910. 
22 . Strasburger, E. : Ueber die Individualitat der Chromosomen und die Pfropfhybriden-Frage. 
Pringsh. Jahrb. f. wiss. Bot., Bd. xliv, p. 482. 
23. Sykes, M. G. : Note on the Nuclei of some Unisexual Plants. Ann. Bot., vol. xxiii, p. 341. 
24. Takara, M. : Ueber Kernteilung bei Morus. Bot. Mag. Tokyo, vol. xxiv, p. 281. 
explanation of plates XVIII AND XIX. 
Illustrating Mr. T. Reed’s paper on the Nature of the Double Spireme in Allium Cepa. 
All figures were drawn with camera lucida under a 2 mm. apoch. horn. imm. Swift obj. and oc. 
12 and 18. Magnification x 1450 and x 2100. 
PLATE XVIII. 
Fig. 1. ‘Resting’ stage, showing chromatin in nucleoli; lower nucleolus shows fibres joining it 
to faintly staining nuclear reticulum, x 1450. 
Fig. 1 a. Nucleoli with crystalline bodies, x 1450. 
Fig. 1 b. Nucleus with bilobed form, x 1450. 
Fig. 2. Early prophase showing commencement of spireme formation, x 1450. 
Figs. 3-4. Later stage of same, x 1450. 
Fig. 5. Spireme with prominent nucleolar connexions, x 1450. 
Fig. 6. Later stage of same ; nucleolus with crystalline body, x 1450. 
Fig. 7. Spireme, showing close relation with nucleolus, x 1450. 
Fig. 8. Spireme with well-developed fission, x 1450. 
Figs. 9-13. Segmentation of spireme to form subdivisions, x 1450. 
Figs. 14, 15. The full number of somatic chromosomes formed, x 1450. 
Figs. 16,17. Pairing of chromosomes on equatorial plate as seen in polar view. 16 x 1450. 
17 x 2100. 
Figs. 18, 19, 20. Metaphases showing the opening of the fission which will effect the separation 
of the daughter chromosomes, x 1450. 
Fig. 21. The chromosomes showing development of ‘vacuoles’ which will bring about their 
fission, x 2100. 
Figs. 22 a and 22 b. Hooked chromosomes (a) from a metaphase, ( b ) from an anaphase. 
X 2100. 
