Stevens. — Spore Formation in Botrychium virginianum. 473 
EXPLANATION OF PLATES XXVIII-XXX. 
Illustrating Professor W. C. Stevens’s paper on Botrychium. 
PLATE XXVIII. 
Fig. 1. Spore-mother-cell in early prophase, x 1800. 
Fig. 2. The same, showing spireme applied to nuclear wall, x 1800. 
Fig. 3. Later prophase-stage showing greatly thickened nuclear thread, x 1800. 
Fig. 4. Chromosomes from various points of view immediately after the segmentation of the 
nuclear thread, x 1800. 
Figs. 5, 6. Later prophases than Fig. 4, showing chromosomes contracted and thickened and 
lines of cleavage no longer recognizable, x 1800. 
Figs. 7, 8. Prophases showing the beginning of the formation of the spindle within the nuclear 
cavity, x 1800. 
Figs. 9-12. Various stages in the development of the multipolar spindle, x 1800. 
Figs. 13-15. Stages in the fusion of the multipolar spindles to form bipolar spindles, x 1800. 
Figs. 16, 17. Late prophases with bipolar spindles, x 1800. 
Fig. 18. First metaphase, x 1800. 
Fig. 19. Polar view of nuclear plate, x 1800. 
Fig. 20. Polar view above nuclear plate showing trans-section of the spindle-fibres. X 1800. 
Fig. 21. Chromosomes culled from stages represented in Figs. 16 and 17. These indicate that 
transverse fission has taken place following the stage shown in Fig. 4. x 1800. 
Fig. 22. Anaphase of the first division, x 1800. 
Fig. 23. Late anaphase of the first division, x 1800. 
Fdg. 24. Polar view of anaphase of the first division, x 1800. 
PLATE XXIX. 
Fig. 25. Two spore-mother- cells in telophase of the first division, x 1800. 
Fig. 26. Later stage showing daughter-nuclei demarked by nuclear membrane, and beginning 
of dense equatorial zone of cytoplasm, x 1800. 
Fig. 27. A stage still later than Fig. 26. The nucleoli have appeared in the daughter-nuclei, 
and the connecting fibres have nearly disappeared, x 1800. 
Fig. 28. A group of spore-mother-cells after the close of the first division. The daughter- 
nuclei are in the resting-stage. The cytoplasm has become entirely regenerated and the dense 
equatorial region is very apparent, x 1800. 
Fig. 29. Early prophase of the second division, x 1800. 
Figs. 30, 31. Later prophase stages of the second division. In Fig. 31 the spindle-fibres are 
becoming evolved within the nuclear cavity, x 1800. 
Fig. 32. A succeeding stage showing a multipolar spindle, x 1800. 
Figs. 33, 34. Metaphases of the second division. In Fig. 33 the nuclei are dividing in the same 
plane, and in Fig. 34 in planes at right angles to each other, x 1800. 
Figs. 35, 36. Anaphases of the second division. 
Figs. 37, 38. Telophases of the second division, showing the origin of the secondary connecting 
fibres from the dense equatorial cytoplasm of Fig. 28. x 1800. 
Fig* 39. Completion of formation of granddaughter-nuclei, x 1800. 
Fig. 40. Beginning of formation of cell-plate, x 1800. 
Figs. 41-43. Completion of cell-plates of second division, and gradual transition from the 
fibrillar condition of the connecting fibres to the alveolar condition of the general cytoplasm, x 1 800, 
