200 The Living Plant 



laboratories, and never without exciting an interested attention 

 from all students, young or old. Some of the results are shown 

 vividly in the accompanying photograph (figure 68), wherein the 

 plant, with its pot and soil enclosed water-tight for this study, 



Fig. 68. — A potted Sunflower prepared for transpiration studies as described in the text. 

 The measuring glasses show the number of cubic centimeters, and therefore of grams, 

 of water transpired in twenty-four hours and in a week. In three and a half days the 

 plant transpired a quantity of water equal to the capacity of the pot in which it is 

 growing. 



is shown standing beside measuring glasses which display the vol- 

 ume of its transpiration for a day and a week. The quantity of 

 transpiration must necessarily depend on the size of the plant ; and 

 in order to compensate this variable, and at the same time to 

 permit a comparison between different plants, it is customary 



