VI CONTENTS. 



PAGE 



Photosynthesis 37 



Physical properties of chlorophyll 39 



Division of the spectrum .40 



Product of photosynthesis 41 



IV. RESPIRATION AND OTHER FORMS OF METABOLISM. 



Nature of metabolism )3 



Respiration -13 



Absorption of oxygen and excretion of carbon dioxide . . . .44 



Liberation of heat ... 45 



Respiration essential to growth 46 



Fermentation . 47 



Changes in color 49 



V. IRRITABILITY. 



Nature of irritability 50 



Perceptive zone, motor zone ......... 50 



Geotropism . . . . . . . . . . . . .51 



Perceptive and motor zones of roots ........ 52 



Amount of influence of gravity 54 



Replacement of gravity 55 



Heliotropism, thermotropism, etc. ........ 57 



Periodic movements ........... 61 



Hydrotropism ............ 62 



Contact movements ........... 62 



Circumnutation ............ 66 



Hygroscopic movements 66 



VI. GROWTH. 



Nature of growth 68 



Grand period of growth 70 



Influence of light on growth 72 



Influence of light on anatomy of leaves 73 



Influence of light and gravity on the formation of organs . . .74 



Influence of temperature on growth 75 



Sources of heat 76 



Relation of temperature to distribution . . . . . . .76 



Freezing of plants ........... 77 



Relation of moisture to freezing 78 



Loss of heat 80 



Resting period 80 



Correlation processes .......... 81 



Mechanical force exerted by growing organs 81 



-Appendix 84 



Jndex 87 



