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DUNCAN S. JOHNSON 
Fig. 22. Surface view of spike, showing young fruits and stamens with un- 
opened and with empty anthers (glycerine mount). X 12. 
Fig. 23. Longitudinal section of fruit with terminal spike and two lateral 
axillary buds. X 27. 
Fig. 24. Longitudinal section of apex of a spike, showing growing point of 
stem and three floral bracts, in the axils of which carpels are being initiated, as is 
indicated by the bulging and deeper staining of cells. X 166. 
Fig. 25. Longitudinal section of floral bract with young ovary. X 216. 
Fig. 26. Transverse section of base of bract through young ovary and stamens. 
X 216. 
Fig. 27. Transverse section of stamen of the age shown in last figure. X 405. 
Fig. 28. Transverse section of bract with half grown ovary and stamens. X 63. 
Fig. 29. Longitudinal section of young stamen. X 540. 
Fig. 30. Transverse section of slightly older stamen. X 540. 
Fig. 31. Transverse section of stamen showing three-layered wall, definitive 
tapetal layer, and young pollen mother-cells. X 315. 
Fig. 32. Transverse section of stamen with nuclei of pollen mother-cells in 
synapsis. X 3i5- 
Fig. 33. Longitudinal section of nearly mature stamen. X 148. 
Fig. 34. Transverse section of nearly mature stamen. X 148. 
Fig. 35. Transverse section of stele of axis of spike, midway its length. X 360. 
Fig. 36. Section of mature pollen mother-cell, just before the beginning of 
synapsis. X 1,300. 
Fig. 37. Section of pollen mother-cell at the beginning of synapsis. X 1,315. 
Fig. 38. Similar section showing later phase of synapsis. X 900. 
Fig. 39. Similar section showing complete synapsis. X 900. 
Fig. 40. Similar section showing beginning of recovery of nucleus of pollen 
mother cell from synapsis. X 1,315. 
Fig. 41. Similar section showing beginning of formation of chromosomes. 
Spireme double. X 1,315. 
Fig. 42. Similar section showing part of chromosomes in first division of pollen 
mother-cell. X 1,315. 
Fig. 43. Transverse section of spindle of first division of spore mother-cell, 
showing form of chromosomes in equatorial plate. X 1,315. 
Fig. 44. Section of pollen mother-cell showing the daughter nuclei organized 
after first division. X 1,125. 
Fig. 45. Similar section showing four pollen nuclei still connected by fibers. 
X 1,315. 
Fig. 46. Similar section showing tetrad of young pollen grains. X 900. 
Fig. 47. Section of uninucleate pollen grain, with large central vacuole and 
partly thickened wall. X 1,315. 
Fig. 48. Section of older pollen grain showing numerous small vacuoles. 
X 1,315. 
Fig. 49. Section of pollen grain with spindle for division into pollen tube nucleus 
and generative nucleus. X 1,315. 
Fig. 50. Section of pollen grain showing generative nucleus with some cyto- 
plasm cut off by cell wall. X 1,315. 
Fig. 51. Section of mature pollen grain still showing faintly the outline of the 
generative cell. X 1,315. 
