4 THE PLANT WORLD. 



the old cup and the installation of the new one). This test 

 showed that the two cups agreed within about one per cent., 

 an amount of error which is negligible for work of this kind. 

 This shows that six weeks of use, the evaporation of 842 

 cubic centimeters of water in this Instance, had no appreciable 

 effect upon the porous structure of the cup. This Is one of 

 several similar tests which lead me to believe that the porous 

 cups here used may be regarded as reliable for an Indefinite 

 period of use when only distilled water Is passed through 

 them. 



This series of observations was continued from July 22 to 

 October 14, a week having been lost between restandardiz- 

 ing the new cup and placing it in the shade exposure. The 

 corrected data, in cubic centimeters, are given in the two fol- 

 lowing tables, the first of which includes the comparative 

 records up to June 17, and the sunshine records to July 22, 

 and the latter those from July 22 to October 14. In the 

 third line of each table are given the ratios of the rate In 

 sunshine to that In shade for the respective weeks. The 

 march of this ratio shows clearly the effect of leaf develop- 

 ment in the early summer and of leaf fall in autumn. 



TABLE L 



Week ending. Stinshine. Shade. Ratio. 



May 27 ', 220 112 1.9 



June 3 62 10 6.2 



June 10 142 54 2.6 



June 17 143 55 2.6 



June 24 141 



July I 146 



Julys 196 



July 15 188 



July 22 202 



