JO Wilson and Greenman. — Movements of the Leaves of 



the same time those in the moister locations below place their 

 leaves so as to receive the sun's rays much more nearly at 

 right angles with the plane of the leaves. 



Experiment No. 2. — Two vigorously growing plants were 

 placed near together on the lawn. Over one was built a glass 

 case, the other was left standing in the open air. The one in 

 the case was soon in a nearly saturated atmosphere. The light 

 was the same in each case. PI. XI, Fig. I shows the one in 

 open air; PI. XI, Fig. % the one surrounded by glass. The 

 stomata were nearly all closed in the first case, while in the 

 latter most of them were open. 



Experiment No. 3. — Three healthy plants were placed near 

 each other on the lawn. The first was allowed to stand free 

 in the open air ; over the second was built a double glass case 

 with two inches space between the walls, filled with alum 

 water to absorb the heat rays of the sun ; over the third was 

 built a single glass case, which was packed with ice in the 

 interior to keep the temperature down. On an extremely hot 

 morning at nine o'clock all three plants were photographed. 

 The temperature was about 8° C. lower under the alum water 

 and in the iced box than around the plant in the open air. 

 The conditions of light were as nearly as possible the same 

 for all three plants. PI. XII, Fig. 1 shows the one in open air, 

 photographed, as are all the others, from the south thirty de- 

 grees west. The leaves are all pointing rigidly toward the 

 sun. They make in this way the least possible shadow, or, 

 in other words, expose the least possible surface to the sun 

 and receive less of its heat rays. In this way transpiration 

 becomes greatly lessened. The stomata are all closed with- 

 out exception. PL XII, Fig. 2 shows the plant under alum 

 water. The leaves are not nearly so elevated as in the first, 

 many of the old ones being so disposed as to receive all the 

 light they can get, while only the very young ones are well 

 elevated and pointed toward the sun. 



In the third one under glass and packed in ice (PI. XII, 

 Fig. 3) the leaves are somewhat more elevated than in the 

 last, but not to be compared with the one in open air. The 

 temperature was a little higher than the one under alum. 



