[ xix ] 



CONTENTS 



PAGES 



AUTHOR'S PREFACE v-viii 



PREFACE TO THE ENGLISH EDITION ix 



A. F. W. SCHIMPER : AN APPRECIATION x-xvii 



FIRST PART. THE FACTORS 



CHAPTER I. WATER 



i. The Vegetative Organs of Terrestrial Plants. i. General Considerations. 

 Hygrophytes and xerophytes. Ombrophoby and ombrophily. Physical and physiological 

 dryness. Characters of tropophytes. Climatic and edaphic xerophytes, hygrophytes, and 

 tropophytes. ii. Xerophytes. Factors reducing the absorption of water. Factors favouring 

 transpiration. Xerophilous structure. Protective means against the loss of water. Correlations 

 among xerophytes of different habitats, iii. Hygrophytes. Wiesner's and Lothelier's researches. 

 Hygrophilous structure. Removal of superfluous water : dripping points, hydathodes. iv. 

 Tropophytes. Tropophilous structure. Leaf-fall. 2. Vegetative Organs of Aquatic 

 Plants. Change in structure of submerged terrestrial plants. Characteristics of true aquatic 

 plants. 3. Water and Reproduction. Hostile influence of moisture on sexual reproduction. 

 Sexual reproduction in aquatic plants. 4. Water and the Dispersal of Seeds. Adaptations 

 of fruits and seeds for dispersal by water-currents. Marine drifts. The new flora of 

 Krakatoa ................ I_ 34 



CHAPTER II. HEAT 



1. General Considerations. Heat and the structure of plants. Effects of a cold climate 

 on the form and lie of leaves. The three cardinal points. Phaenology. 2. Zero Points of 

 Plant-life. i. Lower Zero Points. Power of resisting cold. Death by cold often due to 

 drought. The coldest points on the earth, ii. Upper Zero Points. Power of resisting heat. 

 Sachs' researches. Hot springs. Highest observed temperatures in soil and air. 3. Cardinal 

 Points of the Functions of Plants. The harmonic optimum. The absolute optimum. The 

 oecological optimum. Fluctuations of the harmonic optimum during development. The oeco- 

 logical optima of a peach-tree. Cardinal points of germination. Germination, growth, assimi- 

 lation, and respiration at low temperatures. Useful low temperatures. Effects of cold on sexual 

 reproduction. 4. Acclimatization. Transference from a warm to a cold climate and the 

 reverse. Schuebeler's and A. de Candolle's researches. H. Mayr on the acclimatization of 

 forest trees ............... 35—53 



CHAPTER III. LIGHT 



1. General Considerations. Importance of light in phyto-geography. 2. Photometric 

 Methods. Wiesner's work. 3. Plant-life in Darkness. 4. Intensity and Quality of 

 Light. Effects of light of various intensities on the different functions. Harmfulness of light 

 of high intensity and the corresponding means of protection. Unequal action of different kinds 

 of rays. Absolute and oecological optima of light. 5. Sun and Shade. Full light, light 

 from above, light from the front, light from behind, light from below. Direct sunlight and 

 diffuse light. Wiesner's determination of the actual photic ration of plants. Unequal demands 

 made on light by sun-plants and shade-plants. Contrivances for concentrating light possessed by 

 shade-plants. 6. Day and Night. Phyto-geographical significance of the unequal duration of 

 daylight. Bonnier's investigations with continuous illumination ..... 54~68 



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