354 
The Philippine Journal of Science 
1918 
These facts led us to undertake an experiment to determine 
what changes occur in the length of stems of Oestrum nocturnum 
during the day and the night. The young shoots of this plant 
appear to respond very quickly by curvature to changes in their 
water content. When fully turgid at night the stems bend 
upward slightly. Early in the day they become less stiff and 
assume a straight position. This on dry days is followed by 
a downward bending until they hang down in a markedly wilted 
condition. Later in the day, when they are no longer exposed 
to direct sunlight, they straighten and either late in the after- 
noon or early at night again become slightly bent upward. 
These various changes in curvature may probably be taken to 
indicate the presence of different amounts of water in the shoots. 
The two plants used in the experiment were in a yard in Ma- 
nila and were between two houses; owing to their position the 
time of exposure to direct sunlight was different for the two. 
In order to measure the changes in the length of a shoot, an 
ink line was placed as near as could conveniently be done to 
the growing apex, and another farther back, in a region where 
elongation had apparently ceased. The distance between these 
two lines was then measured at intervals during the day and 
night. 
On one plant four shoots were selected for such measurement. 
A Livingston white spherical atmometer was placed near these 
four shoots, in such position that its exposure to direct sunlight 
was practically the same as was that of the four shoots. A 
thermometer was placed in the shade near the shoots and read 
at the same time that the measurements were made. Measure- 
ments were begun at 12.30 in the afternoon, April 29, 1918, and 
continued until 8.00 in the evening, the following day. The 
results of these measurements, together with observations on 
environmental conditions and on the appearance of the shoots, 
are given in Table I. The evaporation, reduced to Livingston’s 
standard, is given in cubic centimeters per hour. The period 
covered by the evaporation reading for any particular hour 
begins at the time of the preceding measurement. 
When the first measurements of length were made all of the 
shoots were in the shade, and they continued so until dark. At 
8.00 in the morning of the following day they were exposed to 
direct sunlight, and continued to be so exposed until after 11.00 
in the morning, when the sky became overcast with clouds. Dur- 
ing the afternoon the sun again shone brightly, but by this time 
the plants were in the shade of a building. At 12.30 in the after- 
