138 Taylor — A Morphological and Cytological 



Fig. 91. Twin Embryo, Acer platanoides, showing cells of the smaller 



embryo. X200. 

 Fig. 92. Ditto, showing attachment region of the embryos. X200. 



Plate XI — Dicotyledonous and Tricotyledonous Seedling Structure in Acer 



rubrum. All Figures X30. 

 Fig. 93. Dicotyledonous seedling section through lower part of blade of 



cotyledons. 

 Fig. 94. Ditto, section through upper part of cotyledonary petioles. 

 Fig. 95. Ditto, through junction of cotyledons with hypocotyl. 

 Fig. 96. Ditto, just below cotyledonary node. 

 Fig. 97. Ditto, a little lower than Fig. 96. 

 Fig. 98. Ditto, through middle region of hypocotyl. 

 Fig. 99. Ditto, at top of transition region near base of the hypocotyl, 



showing bundle ring. 

 Fig. 100. Ditto, lower, showing passage of xylem toward the periphery 



at four points, in the top of the root. 

 Fig. 101. Ditto, lower, in main root axis, showing tetrarch character. 

 Fig. 102. Tricotyledonous embryo, section through lower part of blade 



of cotyledons. 

 Fig. 103. Ditto, through junction of cotyledons with hypocotyl. 

 Fig. 104. Ditto, just below cotyledonary node. 

 Fig. 105. Ditto, through middle region of hypocotyl. 

 Fig. 106. Ditto, through top of transition region near base of the hypo- 

 cotyl, showing bundle ring. 

 Fig. 107. Ditto, lower, showing passage of xylem toward the periphery at 



four points, in the top of the root. 

 Fig. 108. Ditto, lower, in main root axis, showing irregular tetrarch 



structure. 



Note — All drawings of cytological details except stages in the develop- 

 ment of the embryosac were drawn at a magnification of 3,380 diameters. 

 Other details were drawn at lesser magnifications, and all figures except those 

 on Plate XI have been reduced in reproduction to two-thirds of the original 

 size. The figures of seedling structure were drawn at 75 diameters and re- 

 duced to 30 diameters in reproduction. 



