36 TRANSPIRATION IN A DESERT PERENNIAL. 
gram per square centimeter represents the average maximum for leafless 
forms, 0.0079 gram for adult trees in leaf, and 0.0164 gram for green-house- 
raised plants. Experiment VI was omitted from the series because of the 
error in area which has already been mentioned; so also was VIII, because 
it represents readings in the shade and does not show the drop. 
TaBLE 14.—Summary of some of the data from Experiments I to XIII. 
Maximum preced- | Minimum during | Maximum succeed- 
drop in £ ing drop i dae 
ing drop in = rop in =, ing drop in or day. 
Subject. E E Ei 
a T r T 
z T E E T E z T E E T 
Leafless seedling: 
Ex. I. 
10.0040 yer 0.061 |0.0C56 (0.052 |0.072 (0.0028 |0.040 wet 0.0056 
0041 | .034 120 | .0048 
AVeTAge..... 0... eee eee A563} 20042 itis seals cannalicasinuclags xe alse’ ha abecgralcva ec selene 156 | .0051 
Leafless branch of tree: 
Ki Ts ccctatnspinsecanigndicveahe Sis 151 | .0057 | .038 | .068 | .0034 | .049 | .075 | .0038 | .050 | .151 | .0060 
BNx: DED sacha -an cetincun aoe 158 | .0035 | .038 | .C69 | .0081 | .044 | .078 | .0038 | .049 | .158 | .0043 
AVECTABe. 1. eee eee -155 | .0046 |...... .069 | .0033 }...... .077 | .0038 |...... 155 | .0052 
Branch of tree in leaf: 
Ex. IV 
raised, Ex. IX.. .426 | .0174 | .047 | .445 | .0193 | .050 | .459 | .0225 | .049 | .459 | .0225 
Potted Hane No. 2 
raised, 387 | .0159 | .041 | .387 | .0168 | .050 | .404 | .0198 | .049 | .404 | .0198 
lie ar 317 | .0180 | .041 | none | .0130 | .050 | none | .0152 | .049 | .317 | 0152 
AVOTABC gcse ckcdcis 8: geeky 414 | .0164 |......).0.0.. O160) | sessilis atabceeleniens 428 | .0192 
Potted plant No. 4, transplanted 
from open, Ex. IX............ -158 | .0049 | .031 | .056 | .0023 | .047 | .195 | .0096 | .049 | .195 | .0096 
The maxima for experiment IX have been reduced to white-atmometer maxima by multiplying them by 
1.162, a correction factor which was found by averaging the results obtained by dividing the brown-atmometer 
readings by the corresponding white-atmometer readings on July 27 and on August 5. (See experiment X.) 
Considering only those experiments on plants growing under natural con- 
ditions which show a definite drop and rise in both the actual and relative 
transpiration, it appears that the maximum of actual transpiration reached 
after the dropis in five cases lower than the one before the drop, and in two 
cases the later maximum is about the same as the early one, while in no case 
is the second one higher than the first. It therefore appears that, for a 
certain form under similar conditions, there is a maximum water-loss beyond 
which the plant does not go and that this is frequently reached without a 
previous decrease in the relative rate. In the case of green-house-raised 
plants, where, as has been pointed out, the drop is replaced by a lessening of 
the increase of relative rate and is followed by an abrupt increase in relative 
rate, it appears that while there is a tendency toward a constant value for 
the actual transpiration immediately preceding diminution in the increase of 
the relative rate, yet it is not so marked as in the case of plants in situ. In 
