SUMMARY 
Adaptation in corn is looked upon as the fortuitous or 
chance modification or acquisition of hereditary characters or 
qualities thru the favorable reaction of the crop to its environ- 
ment. This may occur thru, (1) mutation from an individual, 
thus producing a new character; (2) Mendelian recombination 
of unit characters resulting in new forms; and (3) segregation 
of the more suitable types present in a mixed population. Sur- 
vival of the fittest is the active selective principle. 
Nebraska’s climate is very diversified and affords a splen- 
did opportunity for studying the regional adaptation of corn. 
Soil differences are not nearly so great a factor in this adaptation 
as is climate. 
As extremes in climatic conditions, western Nebraska com- 
pared with eastern Nebraska normally has a six-degree F. lower 
temperature during the corn growing season. The frost-free 
period is fifty days shorter, and the precipitation one-half as 
great. The growing season of northern Nebraska is four de- 
grees F. cooler than of southern Nebraska, and the frost-free 
period is about twenty days shorter. The precipitation from 
north to south is rather similar. Much of the country south of 
the Platte River is subject to occasional hot winds which are far 
less common north of this river. No statistics are to be had 
regarding the evaporation rates for various parts of the State, 
but experience indicates that the evaporation rate decreases 
from south to north. This increases the effectiveness of the 
rainfall. 
With an approach from the relatively favorable conditions 
of eastern Nebraska to the combined short season, low tempera- 
ture, and low precipitation of western Nebraska., the native 
corn types assume a more and more dwarfish growth habit. 
The stalks become shorter and bear the ear closer to the ground. 
The total leaf area per plant decreases thru a reduction in 
number, length, and width of the leaves. The ratio of leaf area 
to dry plant substance and the proportion of grain to stover 
remain fairly constant. The ears become shorter, smaller in 
circumference, fewer rowed and frequently are scrubby in ap- 
pearance. The shelling percentage lowers, and the kernels be- 
come shorter and more flinty, as well as slightly lighter in 
weight. 
The leaves, being the seat of transpiration and food syn- 
thesis. might be expected to reflect structural adaptation to ad- 
verse conditions, if such adaptation occurs. Therefore, extensive 
studies of leaf structure have been made. The leaf and epidermal 
thicknesses of native types are fairly constant thruout the State. 
I here is a tendency in the less favored regions for the stomata 
to be somewhat smaller and greater in number per unit leaf 
