CONTENTS 



PART I. GYMNOSPERMS 



CHAPTER PAGE 



I. CYCADALES 1 



The vegetative organs 2 



The stem 2 



The leaf 7 



The root 8 



The spore-producing members 10 



The microsporangium 10 



The megasporangium 14 



The gatnetophytes 19 



The female gametophyte 19 



The male gametophyte . . . ' 23 



Fertilization 28 



The embryo . 30 



II. GlNKGOALES 35 



The vegetative organs 35 



The stem 35 



The leaf 36 



The root 38 



The spore-producing members 38 



The microsporangium 38 



The megasporangium 38 



The gametophytes 41 



The female gametophyte .41 



The male gametophyte 42 



Fertilization 45 



The embryo 48 



III. CONIFERALES 51 



The vegetative organs 51 



The stem 51 



The leaf 60 



The root 63 



The spore-producing members 64 



The microsporangium 64 



The megasporangium 67 



The gametophytes 81 



The female gametophyte 81 



The male gametophyte 89 



Fertilization . .95 



The embryo . . 98 



The classification of conifers 106 



ix 



