CONTENTS 



PAGE 



Chapter I. Introduction i 



Chapter II. Cycadophytes — Cycadofilicales 6 



Distribution 8 



Life-histories ii 



General remarlcs 25 



Phylogeny 28 



Speculative reconstruction 35 



Chapter III. Cycadophytes — Bennettitales 41 



Distribution 42 



Life-history 43 



Phylogeny 59 



Chapter IV. Cycadophytes — Cycadales 60 



Geographic distribution 61 



Chapter V. Cycadales {continued) 76 



The life-history ' . . . . 76 



Chapter VI. Cycadales {continued) 118 



The female gametophyte 118 



The male gametophyte 127 



Fertilization 137 



Chapter VII. Cycadales {continued) 139 



Embryogeny 139 



The seedling 148 



Hybrids 152 



Chapter VIII. Cycadales {continued) 155 



Phylogeny 155 



Taxonomy 161 



Chapter IX. Coniferophytes — Cordaitales 165 



Distribution 166 



Life-history 168 



The sporophyte 168 



The gametophytes 179 



Phylogeny 180 



52578 



