x MORPHOLOGY OF SPERMATOPHYTES 



CHAPTER PAGE 



IV. GNETALES 112 



The vegetative organs 113 



The stem 116 



The leaf 118 



The root 118 



The spore-producing members 119 



The microsporangium 119 



The megasporangium 120 



The gametophytes 124 



The female gametophyte 124 



The male gametophyte . 127 



Fertilization 129 



The embryo 130 



V. FOSSIL GYMNOSPERMS 134 



Cordaitales 135 



Bennettitales 142 



Cycadales 150 



Ginkgoales . . . ... . . . . . .150 



Coniferales 151 



VI. COMPARATIVE MORPHOLOGY OF GYMNOSPERMS 153 



The vegetative organs . . .153 



The stem 153 



The leaf 155 



The root 155 



The spore-producing members 156 



The microsporangium 156 



The megasporangium 157 



The gametophytes 160 



The female gametophyte 160 



The male gametophyte . . . . ' . . . . 162 



Fertilization 164 



The embryo 165 



VII. THE PHYLOGENY OF GYMNOSPERMS 168 



VIIL GEOGRAPHIC DISTRIBUTION OF GYMNOSPERMS 175 



Cycadales 175 



Ginkgoales 176 



Coniferales 176 



Gnetales 178 



SUMMARY OF LITERATURE CITED 180 



APPENDIX 185 



