356 The Philippine Journal of Science ms 
had decreased still further in length. Between 11 o’clock and 
noon, when they were exposed to diffused light, three of them 
elongated 0.5 millimeter, while the other one remained station- 
ary. This latter, however, had elongated 0.5 millimeter during 
the preceding hour. After this all of the shoots were in the 
shade and there was a gradual elongation until 8 o’clock in the 
evening, when all of the stems were again curved upward. 
From the table it will be seen that, as they increased in length, 
they gradually became less wilted. However, at 8 o’clock in 
the evening, when all of the shoots were apparently turgid and 
curved upward, the length was in every case exactly the same 
as at 8 o’clock in the morning, which would indicate that they 
made absolutely no growth during the intervening period. This 
result would, of course, be expected from the wilted condition 
of the shoots which was noticeable throughout the day. The 
elongation during the first afternoon, as the shoots became more 
turgid, was very probably also due simply to their regaining 
the length they had possessed in the morning. If the evapor- 
ating power of air is compared with the measurements of the 
shoots and the condition of the plants, as shown in their 
respective columns, it will be seen that the period of greatest 
decrease in length and greatest degree of wilting did not coin- 
cide with the time when the evaporating power of air was 
greatest ; but that, when the evaporating power of air was great- 
est, the plants were elongating and recovering from wilting. 
Had measurements of evaporation been made with a radio- 
atmometer instead of with a white atmometer, the records 
would in all probability have shown greater coincidence between 
the period of greatest evaporation and that of greatest wilting. 
From the figures in Table I it would appear that the action of 
sunlight on the leaves had a greater effect in producing wilting 
than had the evaporating power of the air, as measured by the 
white atmometer. That the plants did not grow during the day 
but made a fairly rapid growth at night would seem to be related 
to the amount of water contained in them. When the wilting of 
the plants indicated that they were giving off more water than 
they were absorbing, they made no growth. 
Two shoots on the second plant were selected for measure- 
ment. The results for these are presented in Table II in the 
same form as are those in Table I. The evaporation given in 
this table was measured by the atmometer placed near the 
first plant and, as the atmometer was not illuminated in the 
same manner as the second plant, it could not be expected to 
