CONTENTS 



xv 



PAGE 



D. Dry and fleshy fruits 333 



E. Inflorescence fruits 333 



F. Self-planting fruits 334 



G. Seedless fruits 335 



Section 67. The nature of seeds 335 



A. The importance of seeds to mankind . ./ . 336 



B. The importance of seeds to plants . . . 337 



C. Protection of and by seeds 338 



D. Vitality of seeds 339 



E. Structure of seeds 340 



F. Cotyledons and the divisions of seed plants . . 342 



G. Seeds and foods 343 



H. Germination of seeds . . . . . 348 



Section 68. Agencies of seed dispersal ...... 353 



A. Wind 353 



B. Water 355 



C. Animals ...... . 356 



CHAPTER NINE: THE NON-VASCULAR PLANTS 



Section 69. Introductory 360 



Section 70. The four great divisions . . . . . . 360 



THALLOPHYTES : 



Section 71. Algas 362 



A. Unicellular forms ....... 363 



B. Colonial forms 364 



C. Many-celled fresh-water forms .... 365 



D. The groups of algae 371 



Section 72. Fungi 373 



A. Parasites and saprophytes 373 



B. Economic importance ...... 374 



C. Bacteria 374 



D. True fungi 378 



E. Fungi and the soil 391 



F. Lichens 393 



BRYOPHYTES : 



Section 73. Liverworts 395 



A. Reproduction 397 



B. Alternation of generations ..... 401 



C. Leafy liverworts 403 



