Study of Reproduction in the Genus Acer 137 



Fig. 63. Metaphase plate, division in root-tip cell, Acer pseudoplalanus, 



showing fifty-two chromosomes. 

 Fig. 64. Ditto, another case. 

 Fig. 65. Metaphase plate, heterotypic division, Acer pseudo-plalanus, 



showing twenty-six chromosomes. 

 Fig. 66. Ditto, another case. 

 Fig. 67. Metaphase plate, division in root-tip cell, Acer carpinifolium, 



showing apparently fifty-five chromosomes. 

 Fig. 68. Ditto, another case, with the more frequently found number of 



fifty-two chromosomes. 

 Fig. 69. Metaphase plate, heterotypic division, Acer saccharum, showing 



thirteen chromosomes. 

 Fig. 70. Anaphase plate, heterotypic division, Acer saccharum, showing 



twelve chromosomes. 

 Fig. 71. Ditto, other plate in small cell, showing thirteen chromosomes. 

 Fig. 72. Metaphase plate, division in root-tip cell, Acer saccharinum, 



showing fifty-two chromosomes. 

 Fig. 73. Anaphase groups, division in pollen grain to form tube and 



generative nuclei, Acer saccharinum, showing twenty-six and (?) 



twenty-seven chromosomes. 

 Fig. 74. Metaphase plate, division in root-tip cell, Acer saccharinum, 



showing ninety-one (or more) chromosomes, approaching twice the 



normal number. 

 Fig. 75. Ditto, ordinary cell, showing fifty-two chromosomes. 

 Fig. 76. Metaphase plate, division in root-tip cell, Acer rubrum, showing 



ninety (or more) chromosomes. 

 Fig. 77. Ditto, showing eighty-eight (or more) chromosomes. 

 Fig. 78. Ditto, showing ninety-four (or more) chromosomes. 



Plate X — Chromosome Counts and Ovule Development in Acer rubrum, 

 Abnormal Embryo in Acer platanoides (Figs. 79 _8 4 X2250, Figs. 

 85-90 XI35)- 



Fig. 79. Metaphase plate, heterotypic division, showing seventy chro- 

 mosomes. 



Fig. 80. Ditto, showing sixty-eight chromosomes. 



Fig. 81. Ditto, showing sixty-seven chromosomes. 



Fig. 82. Ditto, showing fifty-three chromosomes. 



Fig. 83. Ditto, showing fifty-four chromosomes. 



Fig. 84. Anaphase groups, heterotypic division, showing fifty-two and 

 forty-eight chromosomes. 



Fig. 85. Ovule, resting condition in late autumn. 



Fig. 86. Ditto, at time of synapsis. 



Fig. 87. Ditto, after heterotypic division, showing two cells derived from 

 megaspore mother cell. 



Fig. 88. Ditto, showing row of three potential megaspores. 



Fig. 89. Ditto, showing micropylar two in row degenerating, chalazal 

 cell in the two nucleate stage of the embryo-sac. 



Fig. 90. Ditto, embryosac cell in four nucleate stage. 



