258 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9 
apparent pinna width gradually decreased. To study the relation between 
apparent pinna width and foliar water content, the apparent-width values 
(table I, column 6) were plotted as abscissas of a graph and the average 
actual water contents (table i, column 4) were plotted as ordinates. The 
five graphs obtained in this manner were all approximately straight lines, 
suggesting a linear relationship between the water content per unit of 
Table 2. Hourly Fluctuations in Apparent Pinna Width {for Pinnae Attached to the Plant), 
together with Hourly Temperature and Evaporation Data 
Ave. Apparent Pinna Width 
Evaporating 
Time 
(10 Pinnae on Each Plant) 
Power of 
of 
Temperature 
the Air (White 
Observation 
Spherical 
Plant A 
Plant B 
Plant C 
Atmometer) 
cm. 
cm. 
cm. 
deg. C. 
cc. per hr. for 
April 29 
preceding hour 
6 a.m 
I QzL 
I.QI 
a .y J. 
- 0 
22 
I 81 
1.82 
27 
0.8 
8 a.m 
176 
1-73 
1.97 
29 
1.6 
1.70 
1.69 
1.96 
30 
1-9 
10 a.m 
I '^Q 
1.68 
1.87 
31 
1-7 
II a.m 
T 6^ 
I 6=; 
I 87 
X .U / 
0 
0-0 
12 noon 
1.68 
1.80 
33 
3-6 
I p.m 
T KA 
1.68 
I 7Q 
X . / y 
35 
4-9 
T CD 
T KCt 
T 07 
X .y / 
37 
4-4 
3 P-m 
1 .46 
I =^8 
1.88 
37 
5-1 
4 P-m 
I 6=; 
I =^7 
1.86 
34 
3-6 
5 P-m 
T 78 
I 6=^ 
I 87 
30 
3.8 
6 p.m 
I 87 
1.90 
28 
1-4 
April 30 
I .96 
I q6 
2.26 
23 
T 8/1 
I 8^ 
2.00 
28 
0.9 
1.76 
1-73 
1-97 
30 
1.2 
9 a.m 
1.77 
I 66 
T n 1 
1.94 
32 
2.0 
10 a.m 
1.69 
I '.58 
1.90 
33 
3-2 
II a.m 
1-52 
1-45 
1. 81 
31 
2.7 
12 noon 
I.4I 
1.46 
1-79 
33 
2.9 
1.50 
1.48 
1.77 
35 
4-1 
1.50 
1-59 
1.86 
35 
4-9 
3 P-m 
1.70 
1-55 
1.89 
30 
5-0 
4 P-m 
1-55 
1.48 
1.86 
33 
3-4 
5 P-m 
1.68 
1.70 
1.86 
30 
4.2 
6 p.m 
1.80 
1-75 
1.91 
27 
3-1 
May 2 
2.16 
6 a.m 
2.00 
1.90 
25 
7 a.m 
1.92 
1-79 
2.06 , 
26 
0.7 
8 a.m 
2.01 
1.91 
2.29 
29 
(") 
9 a.m 
1.89 
1.86 
2.08 
27 
(») 
10 a.m 
1.89 
1.78 
2.05 
29 
(«) 
II a.m 
1-73 
1.66 
1-95 
30 
0.8 
12 noon 
1.66 
1.58 
1-94 
33 
2.0 
I p.m 
1.62 
1.46 
1-93 
34 
3-3 
2 p.m 
1-59 
1-49 
1.99 
34 
4-1 
3 P-m 
1.68 
1-44 
1-99 
35 
4.4 
4 P-m -. 
1.62 
1-51 
1-99 
35 
4.0 
5 P-m 
1.58 
1-43 
2.01 
32 
4.0 
6 p.m. . . . 
1.66 
1-57 
2.03 
27 
3-1 
" Rainfall during these hours. 
