942 KirKkwoop: POLLEN-FORMATION IN CUCURBITACEAE 
PLATE 20. Micrampelis 
ates 20 and 21 deal chiefly with the changes taking place in the nuclear struc- 
tures during the first and second divisions of the pollen-mother-cells of A/crampelts. 
Magnification 2,200 diameter 
33. Relatively early oat of the nucleus in mother. cell. 
34. A condition somewhat later than 33. Before synapsis. 
35- a 
36. n of synapsis. 
37. oe ii than 36. Spireme emerging from synapsis and showing longi- 
tudinal ee 
38. pable chromosomes as seen after transverse divisions of the spireme 
ve sein of the nuclei at the stage showing transverse dwitia of the 
spireme. 
42, 43. Showing condensation of the chromosomes. It is at about this time that 
spindle formation begins to be apparent in the cyto 
44. Appearance of some of the chromosomes aoe from various nuclei at about 
the same stage as shown in _ tag 
45. Metaphase of first divisi 
48. Anaphase of first division hawine form of chromosomes and relation of mantle- 
fibers to the same. Int terpolar fibers stain darkly. 
49. Section through mantle-fibers attached to chromosomes; sixteen in number. 
PLATE 21. piece gett 
46, 47. Metaphase of first divisions; heterotypic f 
50. Chromosomes as they appear in the Bictashdine ie ‘be first division attached to 
the fibers. 
RY; bi Chromosomes as they appear in the OM numbering sixteen. 
53, 54. Formation of spireme in telophase of first division 
55- . domaltieat of the nucleus oats at the <diidlaidei of the first division. 
56, 57. Prophase of second divi 
58, 59. Showing persistent elec Deine nuclei in prophase of second division. 
- Anaphases of the second divisio 
63. Pathe acca in telophase of i second division. 
64, 65. Transition from condition shown in 63 to the reticulate resting nucleus. 
Bape Showing transformation from dark cytoplasmic fibers to the extranuclear 
nuclei 
