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 . 



Section 70. The four great divisions . 



360 

 360 



THALLOPHYTES : 



Section 71. Algae 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 



