Feb. 28,1916 
Relation of Stomatal Movement to Infection 
1015 
SIZE) AND MATURITY OF LEAF 
The sizes of the leaves from which the stomatal numbers and pore 
lengths have been taken show a difference that is characteristic of com¬ 
paratively young plants during the early summer. As these plants in¬ 
creased in size, the oldest leaves would for a period be normally much 
smaller than the mature leaves, since the old leaves had been formed at a 
time when the plants were small. This* difference in size is shown in 
Table III, where the mature leaves are much larger (18.3 by 15.1 cm.) than 
the old leaves (10.9 by 7.2 cm.), which in turn are only slightly larger than 
the heart leaves (9.9 by 6.6 cm.). Since the plants had not yet attained 
their maximum size, these heart leaves would, when mature, probably be 
larger even than the present mature leaves. Finally, however, a point 
would be reached where the mature leaves formed would not be in¬ 
creasingly larger with advanced age of the plants, at which time the 
mature and old leaves should be approximately the same size. It thus 
appears that there are great variations throughout the season in the 
sizes of the leaves that are developed at different periods or under abnor¬ 
mal conditions, owing to disease, unfavorable soil factors, etc. However, 
leaf maturity, regardless of leaf size, may be determined by the number of 
stomata per unit area and their pore lengths. 
Table III .—Comparative sizes (in centimeters) of heart , mature , and old leaves and 
cotyledons of the sugar beet. Readings 1 taken at Madison , Wis., on July 6, IQ14 
Heart leaves. 
Mature leaves. 
Old leaves. 
Cotyledons 
Leaf No. 
Length. 
Width. 
Length. 
Width. 
Length. 
Width. 
Length. 
Width. 
J 
18 
17 
17 
2 
18 
% . 
IO 
6 
II 
16 
10. 5 
8*5 
10 
7 
2. 5 
2 - 3 
0. 7 
A . 
14 
IO 
0 
21 
16 
7 
. 7 
» * * * * # * 
c .. 
16 
20 
16 
7 - 5 
3 - 0 
.8 
6 . 
IO 
c 
20 
16 
17 
11 
10 
2. 0 
. 7 
7. 
IO 
5 
6. 5 
IO- 5 
20 
7. 5 
7 
2- 5 
. 7 
8 . 
8 
16 
8 
4 - 5 
5 - 5 
7 
3 - 0 
.8 
0.. 
8 
6. 5 
20 
16 
10 
3 - 0 
1.0 
y 
10. 
8 
6. 5 
20 
16 
10 
2. 0 
.6 
11 . 
IO 
3. 5 
20 
16 
12 
8 
2. 5 
2 * 5 
.6 
12 . 
12.5 
8-5 
7 
20 
16 
12 
8 
.8 
T A 
4-5 
20 
16 
2. 4 
.6 
. 
t e 
.8 
. 
t6 
l8 
15 
13 
IS 
13 
T 1 
12. 5 
6 
l8 
2- 5 
8 
X /.* 
t8 
l8 
■m 
18 
3. 5 
1. 2 
A y . 
20 . 
3. 5 
1. 0 
21 
8 
A 
3.0 
1. 0 
T 
Average . 
9.9 
6.6 
18.3 
15- 1 
10. 9 
7.2 
2. 7 
•2 
1 These leaves were used for the readings given in Tables I, II, and V, and each leaf has the same number 
In all the tables. 
