98 Kansas Academy of Science. 



In the third or sleep position the' leaves sink down, the tips are 

 pointed toward the ground. The two lateral leaflets lie closely 

 against the sides of the terminal leaflet, thus exposing the least 

 possible surface to cold and transpiration. 



The fourth position was brought about by covering the plant 

 with red glass. The sleep position was thus modified some, for in 

 this case the leaves, instead of pointing straight down to the 

 ground, were at an angle and pointed toward the base of stem. 



The author's results have agreed with Wilson's with one or two 

 slight exceptions. I did not perform the experiment with the red 

 glass, but I have noticed the leaves assume that position when the 

 plants were in pots when first taken up, before the root-hairs had 

 grown out again. 



Wilson claimed that it was moisture or transpiration that caused 

 the leaves to assume the hot-sun position. His experiment was as 

 follows : Two potted plants were chosen ; one was covered with a 

 bell jar ; the other was left standing in the open air. The light 

 was the same in each case. The leaves on the plant in the open 

 assumed the hot-sun position; the leaves on the one under the bell 

 jar did not. 



I performed the same experiment several times with potted 

 plants and with plants in the field, without being able to find any 

 difference in the position of the leaves when they were in the 

 saturated atmosphere under the bell jar or in the open air. 



A bell jar was placed over a plant in the field at 8 :30 A. m. By 

 twelve o'clock the atmosphere under the jar was saturated, as shown 

 by the moisture which ran down the sides of the jar. On compar- 

 ing the riumber of leaves which had assumed the hot-sun position 

 with those of a plant standing near by under apparently the same 

 conditions, there was no difference in the number which had turned 

 their tips to the sun. 



The same experiment was performed by covering one branch of 

 a plant and leaving the other open to the air, but no difference 

 could be noticed in the number of leaves which assumed the hot- 

 sun position on the two branches. 



The angles of a number of leaves were taken after they had 

 taken the hot-sun position, and then a bell jar was placed over the 

 plant. In a few minutes the atmosphere under the jar was satu- 

 rated, but no drop from the hot-sun position occurred during one 

 hour and thirty minutes, as shown by the angles. 



A plant was covered with a bell jar at 8 :30 A. m. The air was 

 soon saturated. At eleven o'clock the leaves took up the hot- sun 



