Feb. 38,1916 
Relation of Stomatal Movement to Infection 
1021 
opening (Table VI), and the results agree, in general, with those ob¬ 
tained by Lloyd (6) with desert plants. When the entire leaf was ex¬ 
posed to sunshine, as when the leaf blade stood parallel to the sun's rays, 
the stomata showed the same or a greater pore opening on the lower than 
on the upper leaf surface (series A). This was also found to be true 
with leaves entirely in the shade (series B). When the sun struck ver¬ 
tically upon the leaf blade, an accelerating effect on stomatal opening 
usually resulted, regardless of which surface was exposed to the sun 
(series C and D). This is also in agreement with the work of Balls (1, 
p. 231), in which he found that the stomata on the cotton plant opened 
widely in the sunlight and closed partly in the shade. The leaves in 
series C, read on July 18, indicate a point noticed by Lloyd (7) that 
the stomata near the apex of a leaf might have less pore width than 
those near the base, “a condition readily understandable if wilting is 
progressive from the apex of the leaf downward." 
Table VI .—Effect of sunshine and shade on the width of the stomatal pore opening of 
the sugar-beet plant at Rocky Ford , Colo. } in IQ13 
SERIES A (ENTIRE LEAK IN SUN) 
Date. 
1 
Hour. 
. 
Relative 
humidity. 
Tempera¬ 
ture. 
Stomatal pore width. 
Upper surface. 
! Dower surface. 
0 F. 
May 17 ... 
7.15 a. m. 
58 
67 
i- 8(3) 
1. 8 (4} 
Aug. 4. 
7.30 a. m. 
1 
77 
68 
6 (6) 
“ 7-8 (7) 
SERIES B (ENTIRE LEAR IN SHADE) 
May 17. 
7.15 a. m. 
58 
67 
0 (6) 
0 ( 6 ) 
June 2. 
7.45 a. m. 
100 
65 
i- 5 (8) 
*6.3(8) 
June 3. 
9.30 a. m. 
7 i 
69 
0 
0 
Aug. 4. 
7.30 a. m. 
77 
68 
i -3 ( 7 ) 
4 - 7 (S) 
SERIES c (upper leap surface in sun; lower in shade) 
May 24. 
7.30 a. m. 
69 
68 
4.2 (4) 
8- 6 (s) 
May 26. 
1.45 p. m. 
5 1 
9- 4 (6) 
7- 6 (4) 
May 27. 
8.00 a. m. 
62 
78 
, 4- 5 (4) 
0 (6) 
July 18... 
9.00 a. m. 
9 * 
72 
{ j 5- 7 (3) 
l tf 7* 2 (3) 
* 5 - 7 ( 3 ) 
d 6. 5 (3) 
Aug. 4.s. 
7.30 a. m. 
77 
68 
5 - 7 ( 4 ) 
0 ( 5 ) 
SERIES D (UPPER LEAF SURFACE IN SHADE; LOWER IN SUN) 
May 19. 
8.00 a. m. 
65 
63 
3-8 ( 7 ) 
/ 10. 8 (6) 
May 24. 
7.30 a. m. 
69 
68 
2 . 5 (5) 
3 - 4 ( 5 ) 
May 26. 
1.45 p. m. 
5 i 
9 i 
6. 5 ( 6 ) 
9 - 4 ( 5 ) 
May 27. 
8.00 a. m. 
62 
78 
1. 0 (6) 
7- 4 (6) 
a Wet from dew. 
b All wide open. 
c Apex. 
Base. 
e Many closed. 
1 All open. 
