THERMOTROPISM IN ROOTS 



147 



ily as the sawdust mixture. Two theriiioineters placed side be- 

 side about one centimeter apart showed a difference of three to five 

 degrees. The roots were marked with ink, and the distance from 

 the mark to the tip measured before and after the experiment. 



Experiments With Agar — Ervum Lens Used 



Experiment I. 



T' measured 38°C. throughout the experiment and T' " 13°C. All the roots 

 remained straight except number IV which was slightly bent to one side. Average 

 growth per hour 0.66 mm. 



Experiment IF. 



T' registered 30° andT'" 13°C. Numbers II and VII were bent diagonally in 

 opposite directions. All the others grew perfectly straight. Average growth per 

 hour 0.5 mm. 



