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 . . . . . . . . . . .43 



Respiration ............. 43 



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 



Lpss of heat .80 



Rresting period 80 



Correlation processes 81 



Mechanical force exerted by growing organs . . . . . .81 



APPENDIX 84 



INDEX 87 



