TRANSPIRATION STUDIES. 4 4] 23 
- 003 BS 
ce 2 6 Ue Ur Ue ee 
Fig. 9.—Graphs for transpiration of e, a branch in leaf from an adult tree. 
EXPERIMENT VI. 
The subject of this experiment was a potted plant which had been raised 
from seed in the green-house and then placed in the open for about 4 weeks 
before the beginning of this experiment. At this time the plant was about 
a year old. It is called No. 1 and appears in later experiments under the 
same number. The area was found to be 52.95 sq. cm., but since the leaves 
were not removed for measurement until April 24 a small amount of growth, 
which took place in the meantime, makes the amounts per square centimeter 
in this experiment slightly too small. The movement of the leaves differed 
from that of the trees, in that closing did not begin until after readings had 
been commenced. A record of the position of the leaves appears in this and 
subsequent experiments involving potted plants, in the form of two small 
lines placed below the corresponding readings on the curves. The angle of 
separation of these lines represents the angle of openness of the leaves. The 
relative humidity in the case of all potted plants was taken by a hygrograph 
record and not by the dew-point, as in the case of the bell-jar experiments. 
The atmometer used was No. 850 in the Livingston series and was found to 
be equivalent to 85 sq. em. of free water surface. Plant and atmometer 
