37 o Knight . — Further Observations on the Transpiration , 
The results of such an experiment are given in Table I and Fig. 3. 
Comparative values for ‘ relative transpiration ’ have been obtained by 
dividing absolute transpiration by evaporation, although these values must 
be considered cautiously in the light of the work of Briggs and Shantz ( 4 ). 
They found that atmometers vary considerably in their response to environ- 
mental changes, and that it is not therefore permissible arbitrarily to choose 
any one type of atmometer for calculation of relative transpiration. 
Cribbs (6) also observes that the foliar transpiring index is influenced less 
by wind than is the porous cup atmometer, but it should be pointed out 
that Cribbs used the hygrometic paper method of measuring transpiration 
index, in which air currents are intentionally prevented from reaching the 
cobalt paper and also the portion of the leaf under investigation. The 
present writer, however, has recorded similar conclusions from the results 
of experiments in which the plants were subjected to air currents of known 
velocity ( 13 ). 
Table I. 
Showing the progress of transpiration and stomatal change during the 
early stages of wilting. 
1 
£ Lh’ 
.5 
Period endh 
Relative 
humidity. 
k} ~ 
Actual tra% 
iration ( A . . 
Transpirati 
rate ( 71 ). 
? • 
.ih m 
II 
Absorption 
stem ( A .). 
progressiv 
totals. 
Stomatal 
aperture. 
Mg. 
per 
Mg. 
per 
- 
Min. 
sec. 
°C. 
% 
Mgm. 
T. 
K 
Mg. 
A. 
S. 
min. 
min. 
0 
8 
17.7 
62 
— 
— 
— 
— 
— 
_ _ 
175 
9 
21 
1 7*9 
62 
13.6 
130 
12.3 
0.90 
130 
130 130 
172 
16 
0 
17.8 
63 
15-0 
90 
13*5 
0-90 
no 
240 220 
172 
23 
4 r 
1 7*5 
6 5 
15-4 
no 
14-3 
o -93 
100 
34 ° 330 
171 
32 
16 
17.4 
65 
I 5 , 3 
120 
14.0 
0.92 
130 
470 450 
165 
4 i 
24 
1 7\3 
66 
15*7 
130 
14.2 
0.90 
130 
600 580 
162 
5 i 
14 
17.4 
68 
14.6 
120 
12.2 
0.84 
140 
0 
0 
1^. 
0 
J>. 
159 
61 
10 
17.0 
69 
T 3*5 
no 
1 1. 1 
0-82 ] 
)' 
( 153 
72 
1 
16.7 
70 
13-4 
120 
11. 1 
0-83 
\ 39 ° 
1130 1050 
i x 5° 
82 
58 
16-2 
69 
13-7 
120 
n.o 
0.81 J 
1 
1 148 
W ater- 
supply from potometer stopped. 
93 
47 
15*9 
69 
£3.8 
120 
n. 1 
o-8o ' 
145 
106 
1 2 
16.1 
69 
14.1 
160 
12.9 
0.92 
167 
1 r 5 
53 
15.8 
70 
12.8 
130 
13*4 
1.05 
*94 
121 
47 
I 5 , 9 
71 
12-2 
90 
15-3 
1.25 
208 
128 
■ 7 
J 5-7 
7 1 
II.9 
90 
14.2 
1. 19 
• Nil. 
212 
133 
24 
15.8 
72 
I1..8 
7° 
13.2 
1. 12 
210 
Hi 
52 
l 5-8 
72 
n*9 
100 
11.8 
0.99 
204 
15 1 
6 
15.6 
72 
11. 8 
100 
n.o 
0.93 
195 
159 
16 
15.8 
72 
I 2-1 
80 
9.8 
o-8i , 
190 
The figures in the first column represent the duration of the experi- 
ment from the commencement of observations, the zero point corresponding 
to 1.10 p.m. The stomatal aperture (S.) was gradually diminishing, and 
