THE PHASE OF THE NUCLEUS KNOWN AS SYNAPSIS. 603 



Bbrghs, J., 1904. "La formation des chromosomes heterotypiques dans la sporogenese vegetale" (III. and 



IV.), La Cellule, xxii. p. 43. 

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 Cardiff, J. D., 1906. "A Study of Synapsis and Reduction," Bull. Torr. Bot. Club, xxxiii. p. 271. 

 Davis, B. M., 1909. "Cytological Studies on Oenothera," Ann. Bot., xxiii. p. 551. 

 Duggar, B. M., 1900. "Studies in the Development of the Pollen Grain in Symplocarpus fcetidus and 



Peltandra undulata," Bot. Gaz., xxix. p. 81. 

 Farmer, J. B., and Moore, J. E. S., 1905. "On the Maiotic Phase in Animals and Plants," Quar. Jour. 



Micro. Soc, xlviii. p. 489. 

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Acad. Sci., vi. p. 1. 

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to Mutation," Bot. Gaz., xliii. p. 81. 

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La Cellule, xxv. p. 87. 

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wiss. Bot., xlii. p. 82. 

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and Plants," Ann. Bot., ix. p. 431, 1895. 

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with special reference to the Permanence of the Chromosomes," Ann. Bot., 



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 Sargant, E., 1897. "The Formation of the Sexual Nuclei in Lilium martagon," Ann. Bot., xi., No. 42. 

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EXPLANATION OF FIGURES IN PLATES. 



All the figures were drawn with the camera lucida to the same scale with Zeiss compensating ocular, 

 No. 8, and Zeiss oil imm. obj. 1/12. x 1600. 



Fig. 1. A young spore-mother-cell with the nucleus in the resting stage. The chromatin is in the form 

 of a reticulum composed of very delicate threads. 



Fig. 2. A slightly older stage of the same, showing the first indication of the distension of the nuclear 

 membrane and its withdrawal from the chromatin mass. 



Fig. 3. The same, still older, but here, in addition to the further distension of the nuclear membrane, the 

 chromatin threads of the reticulum are becoming thicker and more sharply defined. 



Fig. 4. The same. An example of the withdrawal of the membrane from all sides of the chromatin mass. 



Fig. 5. The same, showing a further distension of the membrane. 



Fig. 6. The same at a later stage, with a marked change in the development of the chromatin threads. 



Fig. 7. The reticulum has taken the form of a definite spireme. 



Fig. 8. A further withdrawal of the nuclear membrane from the chromatin. The spireme is now sharply 

 defined. The ends of the threads may be seen, as well as the double structure. 



Fig. 9. The same. The pressure within the nuclear cavity is evidently exerting itself equally in all 

 directions. 



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