1911] OVERTON—TRANSPIRATION AND SAP-FLOW 53 
droop in 1-2 hours, and very soon become dry, agreeing in this 
respect with the behavior of the leaves of Bromus hordeaceus. 
My observations support RosHARDT’s conclusions on this point. 
By the method described above, plants growing in nutrient 
solutions may be conveniently sealed in the culture bottles without 
harming the plants, and the amount of transpiration from day to 
day may easily be determined by weighing. In order to ascertain 
whether less water is carried to the leaves after steaming, the rate 
of transpiration during each 24 hours for 5 days was determined, 
_ changes of temperature and the weather conditions being noted; 
then 10 cm. of the stem were killed with steam and the observations 
on rate of transpiration were continued: I have tabulated (tables 
V and VI) the results of such a series of observations. 
TABLES V AND VI 
SHOWING THE EFFECT ON AMOUNT OF WATER goss DAILY BEFORE AND AFTER 
STEAMING I0 CM. OF STE 
TABLE V—OBSERVATIONS BEFORE 
STEAMING TaBLe VI—OBSERVATIONS AFTER STEAMING 
D 
ate — — Weather Date — gira Weather Cencts 
toro | grams| naarate conditions 19I0 grams |perature conditions 
May 18 | 4.0 | 24° C.| Clear May 23 | 1.7 |18°C.} Cloudy} Plant in good 
condition. 
May 19 | 4.7 | 24°C.| Clear May 24 | 1.5 | 25°C.|} Cloudy! Stem above kill- 
ed part with 
ing. 
May 20 | 5.8 | 25°C.| Clear May 25 | 0.9 |19°C.| Cloudy | Leaf tips very 
slightly drying. 
May 21 | 3.2 | 39° C.| Cloudy,|| May 26 | 0.7 |20°C.| Clear | Leaves withered, 
warm ; dry, in- 
rolled. 
May 22] 2.9 | 18°C.| Very May 27 | .0.4 | 23°C.| Clear: | Leaves entirely 
cloudy 1 goa and 
—— ee in 24 || Average transpiration in 24 hours=1.04 grams. 
S=3-9 & 
In tables V and VI the date of the observations is indicated 
in the first column, May 18-22, 1910 (before steaming 10 cm.), 
and May 23-27, 1910 (after steaming). In the second column the 
loss in grams before and after treatment is shown. There is a 
_ gradual decrease in the transpiration loss from 4 gm. to 2.9 gm. 
_ per day in table V, due probably to gradual lowering of the temper- 
