THE FOOD OF THE PLANT 9 



It was not considered desirable to raise the tempera- 

 ture further lest the roots should become injured. 

 The apparatus was then left to regain, gradually, the 

 normal temperature. 



On the following day differences in the rate of ab- 

 sorption, due to varying strengths of the solution ab- 

 sorbed, were tested. 



A strong solution of common salt was made up ; 

 50 cc. of this solution was then added to the water 

 through the thistle funnel. A reading was taken. A 

 second 50 cc. was then added, and another reading 

 taken. By the continuation of this process the strength 

 of the solution inside the jar was gradually increased. 



As it was necessary to make allowance for the de- 

 creasing vitality of the plant due to the continued ex- 

 periment, two readings under normal conditions were 

 first taken. 



Inferences. — -The rate of absorption is affected by 

 external conditions. It increases with rise of tempera- 

 ture ; it also increases as the dryness of the surround- 

 ing air increases. It is decreased by fall of temperature, 

 and by an increase in the strength of the solution ab- 

 sorbed. 



[Note. — Had the apparatus been still further heated 

 it would have been found that, after a certain tempera- 

 ture was attained, the rate of absorption again began to 

 decrease.) 



