42 TRANSPIRATION IN A DESERT PERENNIAL. 
ExrrRIMent XVI. 
The subject of this experiment was an adult tree, called B, growing about 
20 feet from tree A. Transpiration rate was determined by the calcium 
chloride method described on page 10, and the evaporation was determined 
by the use of atmometer of type 2 (C, fig. 2) under aseparate bell-jar. The 
area of the branch used was not determined, so that the T here represents 
actual losses and not losses per unit area. Figure 20 gives the values for 
Vlw plotted with the values for T/E. 
TaBLe 18.—Relative transpiration and stomatal openings from an adult tree. 
Experiment XVI. Date, August 23, 1911. 
Time |e)» vio E : 
3 | BB pcos | seve 
et oe } 0.032 0.235 
24 | 4.4 | .o40] .302 
"3 | 2°53 | ‘050 | 1305 
12 | 31 | [052] [215 
1.4 3.3 048 108 
Experiment XVII. 
Method, Lloyd’s for measurement of stomata. 
Subjects, plants Nos. 1 and 2,and atmometer No. 10, brown. Situation, 
in the open, exposed to sun and wind. Conditions, soil-moisture conditions 
were made to correspond as nearly as possible to those of July 27 and August 
5. No. 1 had been without water 5 days, while No. 2 had received the usual 
amount. The leaves of No. 1 had the same curled appearance as on August 
5, while No. 2 appeared in all respects normal, as on July 27. At the close 
of the experiment, No. 1 responded to water as on August 5. The percent- 
age of soil moisture was determined as before and appears in the tables. In 
this experiment only the widths of the openings of the stomata are given, 
since the curve of widths has been found to correspond in shape to the curve 
of Viw. All measurements were taken in the bright sunlight unless other- 
wise stated. At 6" 30™ a.m. and 12 30™ p.m. measurements were also 
made in the shade and appear on the curvesas isolated dots abovethe corre- 
sponding hours. To the left of the curve appear again, reduced one-half, 
the relative transpiration rates for plants Nos. 1 and 2 under similar con- 
ditions of soil moisture. So far as can be told from the evaporation readings 
for the 3 days, the evaporation conditions were similar. 
TaBLe 19.—Comparison of stomatal openings of potted plants under different 
conditions of soil moisture. Experiment XVII. Date, August 20, 1911. 
Time. No. 1, w.* |No. 2, w.7 | E No. 10. 
shade 1.4 ites “pie 
Geshe Ti. oe Siem 7 8 eis 
9 00 a.m.,sun....... 4 2.8 5.23 
10 00 a.m.,sun....... 0 1.2 6.37 
11 00 a.m., ae Jiiteasi “ re 7.09 
shade ‘ 
12 30 p en ath eB 2 6 } 8.21 
12:00 PAM sess sjencaares 4 1.0 9.05 
* Soil-moisture of No. 1=3.6 p. ct. 
tSoil-moisture of No. 2=14.2 p. ct. 
1Cloudiness prevented further readings. 
