1920] 



SHULLSEEDS 



379 



■ 



is 30 higher than the first, the mean value of Q I0 will be obtained 



extracting 



mean value of Q 



10 



high 



term 



of the ratio is 6 . 1 1 , and its cube root 1 . 83. In both 

 cases the value falls between the coefficient of temperature effects 

 on physical and on chemical processes, but in the last case it 



1 van't Hoff coefficient. These figures are com- 

 he value of Q I0 obtained by Brown and Worley 

 ley have been obtained in exactly the same manner: 



approaches 



Hordeum 



Worley 



1 w 



almost exactly an exponential function of the temperature. If it is , 



TABLE XIII 



Ratios of intake velocities {Xanthium) , 



Data table XI 



Intake 

 percentage 



y 

 y 



y 

 y 

 y 

 y 



= 50 



= 7.5 



= 10. o 



= i5*o 



= 20.0 



= 25.0 



Mean ratios 



Data table XII 



Velocity 20' 



Velocity 5 



Velocity 35* 

 Velocity 20' 



1.88 

 1 .92 

 I.Q7 

 2.08 

 2.l8 

 2.29 



Velocity 20 

 Velocity 5 



Velocity 35' 

 Velocity 20' 



I.72 



1.75 



I.80 



I.83 

 1 .90 

 I.96 



239 

 2.8l 



3.17 



2.71 

 2.92 



2-73 



1. 81 

 1.96 

 2.12 



2.47 

 2-35 

 2-45 



2.05 



1.83 



2.79 



2.19 



logarithms of the velocities plotted against the temperature must 

 lie in straight lines. They show in their second diagram such a 

 plot of the logarithms, and state that the course of the lines in the 

 diagram, in respect both of the straightness and of the agreement of 

 inclination, furnishes evidence of a most conclusive character that 

 the rate at which water is absorbed by barley seeds is an exponential 

 function of the temperature. They call attention to the rarity with 

 which physical properties show an exponential increase with rise in 

 temperature, and then propose that the change is chemical and 

 probably involves a simplification of the water molecule, as 

 already stated. 



The logarithms of the velocity of water intake by Xanthium 

 seeds have been plotted similarly in fig. 3. The curves plotted 



