500 
WALTER L. C. MUENSCHER 
the largest area of stomatal aperture per unit of leaf surface. The 
largest number of linear units of stomatal pore, average of upper and 
lower surface, was found in HeliantJius annuus, 2056 microns, and in 
Zea mays, 1530 microns, while the smallest number was found in 
Pelargonium zonale, 682 microns, and in Impatiens sultani, 731 microns. 
(See Table VI.) 
Table VI 
Showing the Number and Size of Stomata, and the Linear Units of Stomatal Pore in 
Microns per Sqtiare Millimeter Leaf Surface 
Average No. of Stomata 
per Sq. Mm. Surface 
Average Length of Pore 
in Microns 
Average No. of Linear 
Units of Stomatal Pore 
Species 
Average of Upper and 
Lower 
Upper 
Lower 
Upper 
Lower Surface in 
Microns per Sq. Mm. 
250 
40 
8 
1,220 
Ricinus 
121 
52 
10 
10 
865 
lOI 
60 
19 
19 
1,530 
84 
0 
20 
840 
682 
52 
19 
20 
."7 
215 
8 
II 
12 
1,23c 
Impatiens 
29 
9 
6 
731 
21 
46 
34 
39 
i>254 
Helianthus 
172 
71 
19 
14 
2,056 
I now arranged the several species in Table VII in the order of 
their greatest number of linear units of stomatal pore and also placed 
opposite each species in the third column the average amount of 
Table VII 
Showing Relation Between the Amount of Transpiration and Stomatal Aperture 
Linear Units of 
Stomatal Pore in 
Microns per Sq. Mm. 
Amount of 
Transpiration per 
Sq. Dm. per Hour 
in Mg. 
Area of Stomatal 
Aperture in Sq. 
Microns per Sq. Mm. 
of Leaf Surface 
2,056 
156 
6,433 
Zea mays ' 
1.530 
80 
3,864 
Triticum sativum 
1,254 
79 
2,998 
1,230 
65 
2,868 
1,220 
156 
2,890 
865 
209 
1,989 
Primula sinensis 
840 
75 
2,614 
731 
249 
1,705 
682 
50 
1,992 
water transpired per square decimeter per hour in milligrams. This 
average amount of transpiration was obtained from the data in 
Tables II and III. 
