TRANSPIRATION STUDIES. 



23 



6 7 8 9 10 11 12 1 2 3 4 5 



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. cm. of free water surface. Plant and atmometer 



