CONTENTS. 



Introduction ............. 5 



The point of view ........... 5 



The plants studied ........... 7 



Meteorology . . . . . . . . . . . . 14 



Methods ............. 18 



Transpiration ............ 18 



Stomatal action ............ 22 



Effect of caustic potash upon stomata ....... 29 



PART I. 



Transpiration and stomatal movement ... ... . . 31 



Normal daily periodicity .......... 37 



Responses in transpiration and stomatal movement to sudden changes in illumi- 

 nation ...... ...... 45 



Discussion ........ .... 58 



Summary ............. 61 



Induced rhythm in transpiration ......... 64 



Induced rhythm in stomatal movement ........ 74 



Closure of stomata during wilting . . . . . . . . . 81 



Selected experiments ........... 83 



Relative humidity and stomatal movement ....... 88 



Relative humidity its influence upon the condition of stomata ... 88 



PART II. 



Physiology of stomata, with special reference to the metabolism of guard-cells . . 93 

 Normal diurnal changes in contents of guard-cells ...... 93 



Verbena ciliata ........... 93 



Stomatal movement .......... 94 



Oil 97 



Fouquiena splendens .... ..... 102 



Variation in the starch content of the guard-cells ..... 102 



Normal stomatal movement ......... 105 



Summary ............ 



Relation of stomata to certain parts of the spectrum, to darkness, and to air devoid 



of carbon dioxid ........... 108 



Method ............. 108 



The red and blue regions of the spectrum . . . . . . .no 



Red light . . ...... ... .no 



Blue light . . ...... . 112 



Darkness . . . . . . . . . . . .115 



Summary for Verbena .... . . . ... 119 



Additional experiments . . . . . . . . .120 



Experiments with air free of carbon dioxid . . . . . . .121 



Beginning at sunrise ... . . . . . . . .121 



Experiments commencing at time of minimum starch content of guard-cells . 123 

 Discussion and conclusions . . . . . . . . . .125 



General summary ............ 136 



Transpiration and stomatal movement . . . . . . . .136 



Induced rhythm in transpiration . . . . . . . -137 



Induced rhythm in stomatal movement . . . . . . . .138 



Wilting . . ........... 138 



Physiology of the guard-cells . . . . . . . . .139 



Bibliography ............. 141 



