494 
WALTER L. C. MUENSCHER 
amount of leaf surface to begin with, compared with the leaf surface 
at the end of the experiment, the increase being due to growth, I had 
to make a correction for the increased leaf area. I considered the 
increase in transpiration as being proportional to the increase in leaf 
surface and divided the total leaf area by two to find the average leaf 
area during the entire period when the plants were used. This would 
be taking the leaf surface as zero to begin with but this discrepancy 
is balanced by the leaves which died and were removed from the 
plants during the progress of the experiment. This method was 
employed for all of the species which were started from seed. In the 
case of Pelargonium and Primula, two slow growers, where mature 
plants were used, I used the entire leaf surface as was determined at 
the close of the experiment. What little growth took place was offset 
by the loss of several dead leaves which were removed from each 
plant. 
5. The Determination of the Number of Stomata 
For determining the number of stomata I used a Spencer micro- 
scope with a micrometer scale. The value of the scale and of the 
field of the microscope were determined with a stage micrometer. 
The field was divided into quadrants by drawing very fine threads of 
balsam over the eyepiece micrometer. In those plants which had 
an epidermis which could be easily removed I mounted pieces of epi- 
dermis in absolute alcohol and then stained them with a weak solution 
of iodine. In the plants from which the epidermis could not be 
removed readily I counted the stomata "in situ" by the method 
suggested by Lloyd (9). 
The stomatal counts were determined from an average of 30 to 
50 sq. mm. each for the upper and lower surface from five or more 
leaves taken from as many different plants. Only fairly mature 
leaves were used and from these the fields were taken at random on 
the different parts of the surface. 
6. The Determination of the Size and Area of Stomata 
After determining the number of stomata for the several species 
the next process was to determine the size of the stomata for the same. 
In this process I employed the method so successfully used by Lloyd 
(10), Eckerson (5), Renner (11), and Livingston (8), in fixing the 
stomata so that they will not shrink and lose their shape and actual 
