33 
During the following day the transpiration was much slower and too 
abnormal to be worth reporting in detail. The totals for the twenty-four 
hours ending January 19 and January 20 were: 
[a fie | >. | 
en i 
= | 
| Ending—|. A. 
Jan. 19] 4.18 | “#50 ere 
Jan. 20) 1.58) 1.71 1.88 2,02 | 
If now the transpiration of a pinna in situ be computed from the loss 
of weight by pinne in water, and the relative rapidity with which these 
and the former turn cobalt paper red, the following result is obtained : 
| ; l 
Hour. Grams. Remarks, | 
eee ee gene eee. a -e 
POO ASIN) a oe 0.08 | Observed for A. | 
8.30 a.m _____ | 14 | Do. | 
9.80 a.m __..____ 10 | Do, 
| 10.80 a.m _______ . 28 | Do. | 
| 11.30 a.m _______ | .96 | 4/8 by 0.72. | 
fe eee 2 .81 | 4/3 by 0.61. 
} Ca eO DI coo | 3. 02 | 4,25 by 0.71. 
2.30 ppm __----__| 1.19 | 2.75 by 0.43. 
3.30 p.m ________ 1.78 | 3.5 by 0.51. . 
4,80 p.m ________ 1.58 | 17/13 by 1.17 | 
BiO0ip-tn eae ose 91 22/9 by 0.41, 
; Nighie oS loo: | .10 Observed for A. 
Total 2... | 10.30 For one pinna and one 
| day. 
“The free area of leaves furnishing this figure averaged about 120 square centimeters, the rate 
therefore equaling 8.57 grams for 1 square decimeter. Haberlandt (Anatomisch-physiologische - 
Untersuchungen iiber das tropische Laubblatt, Sitzber. Wiener Akad. (1892) 101, I; 804,807) found a 
rate for Cocos at Buitenzorg of 0.89 gram per diem per square decimeter of surface. 
Allowing 150 pinne to the leaf and 25 leaves to the tree, this indicates 
a total daily transpiration for the tree of 38,551 grams. My estimates 
made in this way have ranged ‘between 28 and 45 liters. These calcula- 
tions are based on determinations made on sunny days, and some of them 
are doubtless higher than the average transpiration of the tree for all 
days. On the other hand, it is to be observed that no allowance is made 
for the fact that not all parts of the pinne under experiment were free to 
transpire. 
Another way of combining the cobalt test with the weighing method 
is to use fresh leaves at frequent intervals. This combination offers the 
advantage that the transpiration of the subjects weighed is never very 
much below the normal, but the disadvantage that it is difficult, with such 
a frequent change of subjects, to apply a control based on the continuous 
use of the same pinna. In practice, if the cobalt paper is always applied 
to a fresh part of the pinna, it will turn red once or twice after the pinna 
is cut, at practically the same rate as before. Under ideal conditions this 
method will furnish really accurate results, but the test of a method is 
36512——3 
