xii CONTENTS 



PAGE 



Cessation of photosynthesis on stoppage of light — Molecular 

 strain under photic stress — Partial undoing of positive work on 

 cessation of light — Induction-period and its prolongation under 

 increasing periods of previous darkness — The cyclic curve — Effect 

 of physiological inertia ...-•••• *>3 



CHAPTER XII 



EFFECT OF INTERMITTENT LIGHT ON PHOTOSYNTHESIS 



Further evidence of the intervention of the molecular factor — Effect 

 of intermission on photosynthetic activity under sky light and 

 under Pointolite — Diminution of photosynthetic activity under 

 moderate frequency of intermission — Increased activity under 

 higher frequency — The curve of variation of activity under 

 intermittent light ......••• 9° 



CHAPTER XIII 



THE AUTOMATIC RADIOGRAPH 



The Selenium Cell — Elimination of effect of polarisation — The Wheat- 

 stone Bridge for balance — The automatic keys for periodic 

 closures of circuit— The Galvanograph — Automatic record of 

 hourly variation of daylight — Record on a cloudy day — Simul- 

 taneous records of variation of daylight and temperature; — 

 Light-noon and thermal noon ...... 9° 



CHAPTER XIV 



THE ELECTRIC PHOTOMETER 



The Portable Electric Photometer— Calibration of the Photo- 

 meter — Measurement of widely varying intensities of light — Best 

 aspect of sky for uniform light— Variation of light from northern 

 sky in the course of the day — Sunlight and artificial light . . 108 



CHAPTER XV 



RELATION BETWEEN C0 2 -SUPPLY AND PHOTOSYNTHESIS 



Depression of general physiological activity under C0 2 — Narcotic 

 and poisonous action of excess of C0 2 on photosynthesis— Photo- 



