136 Taylor — A Morphological and Cytological 



Fig. 31. Tapetum cells, showing amitotic nuclear division. X900. 



Fig. 32. Ditto. X900. 



Fig- 33- Tapetum cells, showing mitotic nuclear division. X900. 



Fig. 34. Megaspore mother cell, early diakinesis, showing about thirty- 

 six chromosome pairs. X2250. 



Fig. 35. Row of three megaspores, micropylar pair degenerating, chalazal 

 undergoing nuclear division. 



Fig. 36. Embryosac before migration of the polar nuclei to the center 

 of the embryosac. 



Fig. 37. Meeting of the polar nuclei at the center. 



Fig. 38. Fusion of the polar nuclei after reaching the egg. The nuclear 

 membranes between the nuclei have disappeared. X470. 



Fig. 39. Mature embryosac ready for fertilization. 



Fig. 40. Embryosac shortly after fertilization. One of the synergida> 

 has been destroyed, the other is disintegrating but the nucleus is evi- 

 dent. The dark mass introduced by the pollen tube is present,' and 

 the endosperm nucleus has begun to move toward the center of the em- 

 bryosac. 



Fig. 41. Two cell stage of the embryo, eight nucleate endosperm. 



Fig. 42. Fertilized embryosac before division of endosperm nucleus. 



Fig. 43. Four-celled embryo. 



Fig. 44. Five-celled embryo. 



Fig. 45. Nine-celled embryo. 



Fig. 46. Eight (?) celled embryo. 



Fig. 47. Older embryo. 



Fig. 48. Embryo showing beginning of the two cotyledons. X25. 



Fig. 49. Older embryo of Acer rubrum. X25. 



Fig. 50. Older embryo of Acer saccharinum. X25. 



Plate IX — Chromosome Counts in Various Maples. All figures repro- 

 duced X2250. 



Fig. 51. Upper and lower groups, heterotypic anaphase in Acer negundo. 

 Thirteen chromosomes in each case. 



Fig. 52. Metaphase plate, homotypic division, Acer negundo, showing 

 thirteen chromosomes. 



Fig. 53. Ditto, another case. 



Fig. 54. Metaphase plate, heterotypic division, Acer negundo, showing 

 thirteen chromosomes. 



Fig. 55. Ditto, another case. 



Fig. 56. Ditto, another case. 



Fig. 57. Metaphase plate, division in root-tip, Acer plalanoides , showing 

 twenty-six chromosomes. 



Fig. 58. Ditto, another case. 



Fig. 59. Metaphase plate, heterotypic division, Acer platanoides, show- 

 ing eleven chromosomes. 



Fig. 60. Ditto, another case. 



Fig. 61. Anaphase group, heterotypic mitosis, Acer platanoides, showing 

 eleven chromosomes. 



Fig. 62. Ditto, the other group from the same cell. 



