vi CONTENTS. 



PAGE 



D. Physical and Chemical Processes no 



E. Movements 112 



Section 3. Reproduction 115 



Section 4. Irritability 1 16 



A. Geotropism 117 



B. Heliotropism 128 



C. Hydrotropism 129 



D. Thigmotropism. . . . I3 1 



E. Other Tropisms and Manifestations of Irritability 132 



Section 5. Locomotion 135 



Section 6. Protection 135 



ADDENDA *37 



INDEX . *43 



