viii CONTENTS 



CHAPTER PACK 



XX. THE ALG^E, THE LOWEST GREEN PLANTS 173 



XXI. SUMMARY OF THE LIFE HISTORIES AND EVOLUTION OF THE 



ALG^ 221 



XXII. THE FUNGI AND THEIR RELATION TO FERMENTATION AND 



DISEASE 227 



XXIII. SUMMARY OF THE LIFE HISTORIES AND EVOLUTION OF THE 



FUNGI 272 



XXIV. THE BRYOPHYTES AND THE ESTABLISHMENT OF ALTERNATION 



OF GENERATIONS 275 



XXV. THE PTERIDOPHYTES AND THE APPEARANCE OF HETEROSPORY 306 



XXVI. ALTERNATION OF GENERATIONS 345 



XXVII. HETEROSPORY 351 



XXVIII. THE SPERMATOPHYTES AND THE SEED HABIT 354 



XXIX. THE EVOLUTION OF THE SPOROPHYTE AND DEGENERATION 



OF THE GAMETOPIIYTE . . . 402 



PART III 



ECOLOGY AND ECONOMIC BOTANY 



XXX. PARASITES AND CARNIVOROUS PLANTS 407 



XXXI. How PLANTS PROTECT THEMSELVES FROM ANIMALS . . . 413 

 XXXII. POLLINATION OF FLOWERS AND PROTECTION OF POLLEN . . 420 



XXXIII. How PLANTS ARE SCATTERED AND PROPAGATED 436 



XXXIV. SOCIAL HABITS OF PLANTS; COMPETITION AND INVASION . . 447 

 XXXV. PLANT SUCCESSIONS 454 



XXXVI. ECOLOGICAL GROUPS AND THEIR CHARACTERISTICS . . . 459 



XXXVII. PLANT FORMATIONS ; ZONATION 474 



XXXVIII. PLANT GEOGRAPHY 481 



XXXIX. VARIATION, MUTATION, AND ORIGIN OF SPECIES .... 496 



XL. PLANT BREEDING 500 



XLI. SOME USEFUL PLANTS AND PLANT PRODUCTS ...... 514 



APPENDIX 537 



INDEX . . 541 



