go BOTANICAL GAZETTE [AUGUST 
were then placed in the greenhouse and were watered from time to 
time. A Livingston standard atmometer of the cylindrical form 
was set up in close proximity to measure evaporation. Readings 
were taken of the atmometer whenever a reading was made of the 
transpiring power. On July 1g the plants were thoroughly watered 
and were lightly watered again on July 20. On July 21 the con- 
tainers were sealed over with plasticine preparatory to making 
hourly readings of the foliar transpiring power for a period of 
twenty-four consecutive hours. For the measurements upon the 
index of foliar transpiring power the same apparatus as employed 
before was used. On the 18th hour of July 22 the last reading was 
made for the daily march of foliar transpiring power. Beginning 
July 24, readings were taken three times during the day: (1) at 
approximately 10:00 A.M., (2) at the 14th or 15th hour, and (3) at 
some time during the night. The times chosen really represent the 
three important periods during the daily march, for the first one 
gives this value at a time when the transpiring power is near its 
maximum, the second when evaporation is at its maximum, and 
the third when the index of transpiring power has its lowest value. 
The leaves were tagged as before so that the same leaves were used 
throughout. 
The soil surface of several additional plants was coated over 
with plasticine to serve as a comparison or check for the plants 
used for the determination of foliar transpiring power. In apply- 
ing the cobalt paper squares from day to day, it became easy to 
judge the condition of the plant. When plants presenting a 
physical state such as was in evidence for leaf Ia, on August 3, and 
for leaf Ib, on August 7, were placed in a moist chamber, they failed 
to recover. It was then deemed unnecessary to test further. At 
the time of the beginning of the experiment plant Ia was 25 cm. 
high, while plant Id was 28 cm. high. 
INDICES OF FOLIAR TRANSPIRING POWER 
In using the method of standardized hygrometric paper for 
the determination of the indices of foliar transpiring power, two 
separate plants were used. The method of numbering the leaves 
was the same as for the 1915 series. From plant Ia two leaves 
