xiv LIST OF ILLUSTRATIONS 



FIGURE ^^ 



33-36. Life-History of a Fern 



37. Megasporangium of Selaginella .... 



38. Mega- and Microsporangia of Selaginella 

 39-40. Dioon edule, Longitudinal Section of Ovules 

 41-45. Dioon edule, Development of Archegonium 



46. Male Cone of Ceratozamia 



47-49. Male Sporophylls of Ceratozamia mexicana 



50. MiCROSPORANGiUM OF Dioon edule 



51. Sporangium OF ^wgfa/>/m.s 



52-53. Microspores of Dioon edule .... 



54. Stangeria, Nucellus with Pollen Tubes . 



55. Stangeria, Pollen Tubes with Sperms . . 

 56-57. Dioon edule, Body Cell with Blepharoplasts 



58. Dioon edule, Young Sperms 



59. Ceratozamia, Photomicrograph of Sperm . 



60. Dioon edule. General View of Fertilization 



61. Stangeria, Fertilization 



62. Stangeria, First Division in Fertilized Egg 



63. Dioon edule, Free Nuclear Stage of Embryo 



64. Stangeria, Free Nuclear Stage of Embryo 



65. Stangeria, Simultaneous Nuclear Division 



66. Stangeria, Evanescent Walls of Embryo . 



67. Stangeria, Early Walls in Embryo . . . 



68. Zamia floridana. Young Embryo .... 



69. Dioon edule. Cotyledon Stage of Embryo . 



70. Dioon edule. Section of Seed 



71-73. Dioon edule, Germination of Seed . 

 74-76. Dioon, Margins of Leaflets .... 



77. Dioon spinulosum. Seedling 



78. Diagram of Geological Horizons . 



79. Idealistic View of Primitive Seed Plant 



80. Cycadeoidea, Bisporangiate Strobilus . . 



81. Cycas revoluta. Crown of Female Sporophylls 



82. Dioon edule, Female Cone 



83. Macrozamia Miquelii, Female Cone . 



84. Zamia floridana. Female Cone .... 

 85-91. Female Sporophylls of Cycads . . . 



