ioi 6 
Journal of Agricultural Research 
Vol. V, No. 22 
COMPARISON OP FACTORS FOR DIFFERENT REGIONS 
A comparison of the observations of stomatal numbers and pore 
lengths, leaf size and maturity at different times and places and under 
various conditions indicates the constancy of existing relations. These 
studies have been made in the field in Wisconsin and Colorado and in the 
department greenhouse at Washington, D. C. (Table IV). In general, 
the sizes of leaves are not comparable as read from these three places in 
that the periods of observation were varied and the controlling factors 
were different. However, the variations in the number and size of the 
stomata on the different leaves in a given locality have remained uniform 
in all readings. 
The heart leaves, as would be expected, always exhibited more stomata 
per unit area and had shorter pore lengths than the mature leaves on the 
same plant, and, in turn, the mature leaves showed more stomata per 
unit area than the old mature leaves. It is to be noted, however, that 
heart leaves in Wisconsin, although comparing them with those studied 
in Colorado in stomatal pore lengths, showed twice as many stomata per 
unit area, indicating less maturity and consequently a greater possible 
ultimate development in area of leaf surface. This difference probably 
was due in great measure to the almost constant presence of leafspot 
on the plants observed in Colorado and the great freedom from it in the 
Wisconsin field from which the data were taken. The accumulative 
effect of the disease on the plant would be shown by the development 
of smaller sized leaves with a lessened number of stomata per unit area, 
showing that they were maturing at a size below normal. 
TabeE IV .—Comparison of the average size of leaf , stomatal numbers , and pore lengths 
on different leaves of sugar-beet plants studied in Wisconsin , Colorado , and Washing¬ 
ton, D. C. 
Locality and leaf 
maturity. 
Size of leaf. 
Number of stomata 
per square milli- 
meter of leaf sur¬ 
face. 
Stomatal pore 
length. 
Number 
of leaves in 
averages. 
Length. 
Width. 
Upper. 
Lower. 
Upper. 
Lower. 
Wisconsin : l 
Cm . 
Cm . 
A* 
M 
Heart. 
9.9 
6.6 
289. 8 
353 - 5 
14. O 
14. O 
13 
Mature. 
18.3 
15 - 1 
100. 7 
130. 6 
28. 5 
27. I 
16 
Old mature. 
10. 9 
7.2 
80. 1 
105.0 
3 1 * 1 
30 - 5 
IO 
Cotyledons. 
2.7 
.8 
54 - 7 
73 * 2 
31.8 
32.1 
18 
Colorado : 2 
Old heart. 
IO. 2 
12. 1 
144.9 
206. 2 
6 
Old heart, unin¬ 
fected 3 . 
11.8 
8.6 
145-9 
187-5 
14.4 
14.8 
11 
Young mature, 
infected 3 . 
J 3 * 5 
10.3 
105.9 
142. 8 
17.8 
17. 6 
13 
Mature. 
16 
14.4 
80. 4 
109. 6 
19.4 
18.1 
26 
Washington, D. C.: 4 
Old heart. 
C. 3 
161. 0 
18 
Mature. 
0 O 
6. 7 
O' * 
4 
08. 0 
56 
Old mature. 
6. 0 
T 
4 . 2 
74 - 5 
57 
1 m 
1 The results given are the averages taken from Tables I, II. and III. 
8 Readings made in the field from June to August, inclusive, 1913. 
* The results given are the averages taken from Table X. 
4 Readings made during January, 1914, on potted plants about 8 weeks old grown in the greenhouse. 
