37i 
Dioxide Absorption of Coco-nut Leaves. 
of which between two marks was 25-07 c.c. at 27° C. ; this pipette was filled 
with the solution and emptied three times to wash it before samples were 
drawn for testing. Then three samples of 25*°7 c - c - ea °h were drawn into 
Erlenmeyer flasks, two drops of neutral methyl orange were added to each, 
and they were promptly titrated against a standard solution of hydrochloric 
acid of nearly the same concentration as the barium hydroxide. The 
triplicate titrations agreed with each other within 0*05 c.c. of acid used 
in all except two cases, in which the divergent samples were o-io different 
from the two identical tests. The two identical numbers were assumed to 
represent the correct value. 
Experimentation. 
After a large number of practice trials, tests were begun in May 1918, 
at the beginning of the south-east monsoon, which is also the beginning of 
the rainy season. Immediately preceding this time there was a drought 
extending from December 22, 1917, to May 13, 1918. Thus the vegeta- 
tion was not in active growth at the beginning of these tests. 
Nine series of tests are here reported, each consisting of observations 
during one daylight period. The first of these, Series 1, was a preliminary 
trial with detached sugar-cane leaves. Series 2 to 6 were made on coco-nut 
pinnae attached to the tree. Series 7 was on detached coco-nut pinnae, and 
Series 8 with an attached, and Series 9 with a detached abaca leaf ( Musa 
textilis , Nee). 
All the measurements of attached coco-nut leaves were made on one 
tree, about three years old, growing in an open closely- clipped lawn on 
shallow alluvial soil, in a fiat plain at 55 m. elevation above sea-level. 
It was fully exposed on all sides. The tree was about seven feet high to the 
top of the tallest of its six leaves, and received no special attention, either 
by cultivation or irrigation, during the experiments. 
Series i. — Tests of a half leaf detached from a sugar-cane plant , 
May 1 6 , 1918. 
This experiment was undertaken to learn whether this gas analysis 
method gives approximately the same value for carbon dioxide absorption 
as is indicated by the increase in dry weight per unit area of the leaf, and 
also to get an idea of the effect of the conditions imposed by the apparatus 
on the increase in dry weight per unit area. The dry weight method 
of determining photosynthesis in sugar-cane was found to be inaccurate 
in recent work by Kuijper, 1 who states that in some cases the errors due to 
differences in weight of different parts of the leaf may attain to twenty-five 
1 Kuijper, J. : Proeven over de afhankelijkheid van het assimilatieproces bij het suikerriet van 
de uitwendige omstandigheden. Meded. van het proefstat. voor de Java-suikerind., Landb., ser. 
1917, No. 13. 
