FOLIAR TRANSPIRING POWER OF THE COCONUT: 
By Sam F. TRELEASE 
] 
Of the Johns Hopkins University 
ONE TEXT FIGURE 
The purpose of this article is to describe the results of tests 
on the daily march of transpiring power of coconut (Cocos nu- 
cifera Linn.) leaves, as indicated by standardized cobalt-chloride 
paper. The method used was essentially the same as that 
described by Livingston (6) with, however, some of the modifi- 
cations suggested by Trelease and Livingston,(14) and by 
Livingston and Shreve.(10) Small slips of filter paper im- 
pregnated with cobalt chloride were used; when dry the slips 
are bright blue, but upon absorbing moisture they gradually 
become pale blue, then pale lavender, and finally pink. The 
cobalt-chloride method of determining transpiring power involves 
a determination of'the ratio obtained by dividing the time-period 
for a given color change over a standard evaporating surface 
(water-saturated porous clay covered with a millimeter of air) 
by the time-period for the corresponding change upon the leaf 
surface at the same temperature; the index of transpiring power 
thus obtained shows the relative power of the plant surface 
to give off water vapor, as compared with the corresponding 
power of the standard water surface. In the present tests the 
abundance of moisture in the atmosphere made it difficult to 
use the bright blue color as the initial shade (as recommended 
by Livingston and Shreve), and so the pale blue standard color 
used by the authors just mentioned was employed, the time being 
recorded for the change from the Livingston-Shreve pale blue 
standard to pink. The slips were standardized once for all in 
the laboratory, and each slip was given a coefficient, by which 
was obtained the time-period for the change over the standard 
evaporating surface at each time when leaf tests were made.” 
After standardization the slips were dried and then placed in 
Small desiccators containing calcium chloride. 
* Botanical contribution from the Johns Hopkins University, No. 72. 
“See article by Livingston and Shreve (10) that is cited at the end of 
this Paper. 
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