RELATION OF TRANSPIRATION TO STOMATA 
499 
were taken from several pieces of epidermis from several leaves from 
at least three plants. It was noted that individual stomata of the 
same plant or even leaf vary somewhat in size depending upon the 
part of the leaf in which they are located. 
Table V 
Showing the Length and Breadth of Stomata in Microns 
Name of Species 
Lower Surface 
Upper Surface 
Guard Cell 
Pore 
Guard Cell 
Pore 
Ricinus communis 
Primula sinensis 
20 X 15 
26 X 18 
36 X 27 
42 X 31 
38 X 27 
28 X 18 
20 X 16 
62 X 30 
37 X 26 
8X3 
10 X 3 
19 X 3 
20 X 4 
20 X 4 
11 X 3 
9X3 
34 X 3 
19 X 4 
20 X 13 
22 X 15 
33 X 19 
38 X 27 
30 X 21 
17 X 14 
65 X 29 
30 X 24 
II X 3 
10 X 3 
19 X 3 
Pelargonium zonale i 
Impatiens sultani 
Triticum sativum 
Helianthus annuus 
17 X 3 
12 X 5 
6X3 
39 X 3 
14 X 3 
Upon comparing the results of Tables IV and V, I noticed several 
general facts: 
1. The size of stomata on the same plant may vary considerably 
with the upper and lower leaf surface. 
2. In general plants with few stomata have large ones and plants 
with many stomata have small ones. 
From the data in Tables IV and V, I computed the average number 
of units of stomatal pore length in microns per square millimeters 
of leaf area for the upper leaf surface and for the lower leaf surface by 
multiplying the number of stomata per unit of area by the average 
length of one pore. Then I computed the average number of microns 
of stomatal pore length for the upper and lower surfaces by adding 
the two values and dividing by two. The linear units of stomatal 
pore and not the area of the stomatal pore is important since Brown 
and Escombe (2) have shown that the length of the pore and not 
its area is important in transpiration. 
I also computed the area of the stomatal pore of one stoma and 
then the area of the total amount of stomatal aperture per square 
millimeter, average of upper and lower leaf surface, by considering 
the stomatal pore an ellipse. (See Table VI.) 
The data show that it is not necessarily the plant with the largest 
stomata or the plant with the greatest number of stomata that has 
