118 Nebraska Agricultural Exp. Station, Research Bui. 6. 
hourly. The average transpiration per day was 3,112 grams, 
which is equal to 2.1 grams per day per square inch leaf -area. 
The average evaporation per day was 227 grams, which is equal 
to 6.3 grams per square inch free water surface. 
In this test the transpiration rate per square inch leaf-area 
was 33.3 per cent of the evaporation from a square inch free 
water surface. 
In 1910, the daily transpiration was determined during 30 
days for 12 corn plants after the leaf -area was fully developed. 
Likewise the evaporation from six evaporation jars of 36 square 
inch free water surface at elevations above the ground of 0, 2, 4, 
6, 8, and 10 feet was determined. The total average transpiration 
for one corn plant of 1,209 square inches leaf-area during the 30 
days was 71,277 grams, which is equal to 58.9 grams per square 
inch. 
The total average evaporation for one evaporation jar of 36 
square inches free water surface was 7,363 grams, which is equal 
to 205 grams per square inch area. According to these data, 
the transpiration rate per square inch leaf -area was 29 per cent 
as great as the evaporation from a square inch free water surface. 
As an average for all three tests in 1910 and 1914 we find 
that the evaporation from a square inch of leaf area was 32 per 
cent as great as the evaporation from a square inch of free water 
surface. Since a corn leaf has two epidermal surfaces from which 
water evaporates, one may calculate that the evaporation from 
a given area of free water surface is approximately six times as 
great as from an equal area of leaf surface. 
The above leaf and free water surface evaporation data are 
quite comparable for the reason that the leaf-area was fairly 
constant during the time of the tests. 
At the Nebraska Agricultural Experiment Station an average 
acre of well-adapted corn has two acres of leaves, or 4 acres of 
leaf surface, counting both sides. 
THE GROWING CROP AS A PROTECTION AGAINST WATER- 
DISSIPATING INFLUENCES. 
EVAPORATION STUDIES IN CORN AND SMALL-GRAIN FIELDS. 
For a number of years, botanists have been studying eco- 
logical conditions of natural habitats of native plants. Similar 
principles may be applied in the study of cultivated fields. 
In fact, our study of crop production is largely one of applied 
plant physiology and ecology. Among the least investigated 
features of this field ecology are the water dissipating influences 
as expressed by the evaporation power of the air within the 
