CONTEXTS 



CHAPTER PAGE 



I. — Introductory 1 



Angiosperms and Gymnosperms contrasted, 1 — Spermatophytes 

 not a natural group, 3 — Monocotyledons and Dicotyledons con- 

 trasted, 4. 



IX— The Flower 8 



Definition of a flower, 9 — Origin of floral leaves, 9 — Tendencies 

 in the evolution of the flower, 10 — Organogeny of the flower, 16 

 — Dioecism, 20 — Morphology of floral members, 22 — Stamen, 23 

 —Carpel, 24. 



III. — The Microsporangium 27 



Origin from periblem, 27 — Cauline microsporangia, 28 — Number 

 of microsporangia, 29 — Time of formation, 30 — Development, 

 32 — Archesporium, 32 — Parietal layers, 34 — Tapetum, 36 — 

 M other-cells, 38 — Dehiscence, 41 — Line of demarcation between 

 sporophyte and gametophyte, 41. 



IY. — The Megasporaxgium 46 



Origin from periblem, 46 — Cauline ovules, 46 — Foliar ovules, 50 

 — Morphological nature of ovule, 51 — Time of development of 

 megasporangia, 52 — Development of ovule, 53 — Archesporium, 

 57— Parietal cells, 62— Mother-cell, 66. 



V. — TnE Female Gametophyte 71 



The tetrad, 71 — Number of megaspores, 76 — Reduction of chro- 

 mosomes, 80 — The functioning megaspore, 84 — Number of em- 

 bryo-sacs, 86 — Germination of megaspore, 87 — Variations in 

 history, 89 — Egg-apparatus, 93 — Synergids, 94 — Fusion of polar 

 nuclei, 95 — Antipodal cells, 96 — Enlargement of embryo-sac, 103 

 — The nutritive jacket, 103 — Haustoria, 104 — The mechanism 

 for nutrition, 108. 



VI. — The Male Gametophyte 121 



The tetrad, 121 — Number of microspores, 125 — The nuclear divi- 

 sions of the pollen mother-cell, 126 — The microspores, 131 — Ger- 

 mination of microspore, 132 — Division of generative cell, 135 — 

 The male nuclei, 136. 



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