THERMOTROPISM IN ROOTS 145 



After three more, one at T'" had reacted positively and one more at T' negatively. 

 At this time T' was at 36°C. and T'" at 15°. 



Third Experiment. Conditions identical with the last experiment. After fort)' 

 minutes T' is at 42°C. and T'" at 11°C. After four hours more, six rocfts at T' 

 had bent negatively. After four more, one root at T'" had reacted. T' was now 

 at 4Q° and T'" at 13°C. 



Fourth Experiment. In this experiment the radicles were as before 1.5 cm long 

 and eight seedlings were placed on a side. T" was at 45°C. and T'" at 12°C. in 

 forty minutes. After two hours, five roots at T" were negatively bent. In six more 

 no change occurred and T' was at 46° and T'" at 13°C. 



Fifth Experiment. This time four roots of Ervum Lens were placed on either 

 side. The radicles were 2 cm. long. In forty minutes T' reached 40°C. and T'" 12°. 

 After an hour three of those at T' were negatively bent. No more change in five 

 hours. T'" registered 14°C. and T' 42°C. 



Sixth Experiment: Again eight roots were placed along either side wall and 

 as before the radicles were 2 cm. long. T' reached 38° and T"" was 13° in forty- 

 five minutes. After two hours five roots at T' had reaci-ed negatively. In an other 

 hour two more at T' were bent. After four more hours, one root at T'" was posi- 

 tively bent. T' was now at 37° and T'" at 14°C. 



Seventh Experiment. In the last of these experiments the radicles were 1.5 cm. 

 long. At the end of an hour T' was at 48° and T'" at 14°. One root at T' was al- 

 ready bent. As the light was extinguished no further reaction took place. 



The use of the cover increased the length of time required for 

 the reactions at higher temperatures from an hour or an hour and 

 a half, to three hours. Those roots placed along the cool partition 

 in some cases failed to react at all, and in the other cases only 

 very slowly. 



An attempt was made to see if the roots would react to a ther- 

 motropic stimulus if suspended in saturated air. For this purpose 

 the sawdust was removed from its compactment, and warm water 

 poured in the bottom. The roots were fastened to the cover, and 

 hung down vertically above the surface of the water. No reaction 

 was obtained. If the compartment were filled with water, and 

 the roots immersed in it, in the same way, they grew in every 

 conceivable direction without any bearing to the temperature 

 differences. This, moreover, was found to be temporary, because 

 of currents which soon rendered the temperature of the water 

 equivalent throughout. To avoid these currents, the water was 

 mixed with sawdust, almost to the point of its becoming solid. T' 

 registered 40°C. and T'", 15°C. No bending was obtained. This 

 experiment was repeated as follows: The just fluid mixture of 

 sawdust and water was boiled until all the air was driven out, and 



