The Regional Adaptation of Corn in Nebraska 
29 
of a leaf punch, from the ear leaf of each plant measured. The 
point of sampling was at the widest part of the leaf midway 
between the mid-rib and leaf margin. A quantity of adjoining- 
upper and lower epidermis was also removed and preserved. 
The leaf samples were preserved in absolute alcohol for later 
study. Previous experience had suggested that fairly compar- 
able data might be secured by use of a similarly situated leaf 
from ten different plants of each variety. The number of plants 
studied from any one locality ranges from thirty to sixty, 
representing three to six different farms. The microscopic sec- 
tions were made free-hand by using small corks and a sharp 
razor. An extensive method study proved that the use of only 
a few measurements would be unreliable because of the incon- 
sistencies of leaf structure and, therefore, a large number of 
duplicate counts and measurements were made. An average of 
five varieties were studied microscopically for each of the seven 
counties. Four hundred transectional leaf measurements, and 
160 epidermal counts and measurements were made for each 
variety, averaging a total of 2,000 per county in the former case 
and 800 in the latter. The following measurements were taken: 
Leaf Thickness — This measurement includes the cuticle of 
each epidermal layer. Tissue immediately adjacent to the large 
vascular bundles was avoided. 
Epidermal Thickness — The upper and lower epidermis were 
measured at the same point as the leaf thickness, including the 
cuticle. 
Vascular Bundles — Counts were made of the number of vas- 
cular bundles in the cross-sections of the leaves. 
Number of Stomata in a Unit Area — The number of sto- 
mata were counted in 100 microscopic fields for both the upper 
and lower epidermis of each type. The microscopic fields were 
chosen systematically in order that the results might be repre- 
sentative. 
Length of Stoma and Stomatal Aperture — As far as possible, 
representative stomata were measured. It was at times with 
difficulty that the stomatal aperture was measured. 
Length and Width of Epidermal Cells — Since these and all 
other microscopic measurements were made in eye piece spaces, 
it was necessary to convert them into microns. 
RESULTS 
The results of these histological studies are contained in 
Tables 12 and 13. The various localities are grouped into eastern, 
central, and western Nebraska regions. Since these studies in- 
volve only seven of the twelve counties used in studying the 
