vi CONTENTS 



XXV. Transpiration Affects Plant Development and 



Distribution 233 



XXVI. Forms and External Features of Stems 245 



XXVII. General Regions and Processes in Stems 262 



XXVIII. Tissues and Processes in Stems 278 



XXIX. Roots: Development and Structures 294 



XXX. Roots: Processes and Soil Relations 315 



XXXI. Initiation of Fowers 333 



XXXII. Flowers, Fruits, and Seeds 351 



XXXIII. Sexual Reproduction in Flowering Plants 371 



XXXIV. Growth, Dormancy, and Germination of Seeds 387 

 XXXV. Vegetative Multiplication of Flowering Plants 400 



XXXVI. Origin of Plants Used by Man 423 



XXXVII. Heredity in Plants 438 



XXXVIII. Cross-Fertilization and Hybrid Segregation 458 



XXXIX. Mutations 474 



XL. Types of Variations and Diversity of Organisms 490 



XLI. Non-Green Plants 504 



XLII. The Biology of Bacteria 515 



XLIII, Bacteria of the Soil 531 



XLIV. The Fungi 541 



XLV. Plant Diseases 567 



XLVI. Under-Water Environments 587 



XLVII. The Algae 606 



XLVIII. Mosses and Liverworts 638 



XLIX. Ferns, Club Mosses, and Equisetums 656 



L. The Seed Plants 678 



LI. Some Families of Flowering Plants 693 



LII. Plants of the Past 719 



LIII. The \'egetation of North America 740 



Index 797 



