128 ILLINOIS ACADEMY OF SCIENCE 
by transpiration, measured by the atmometer, controlled by 
thinning or by windbreaks. Temperature is observed by the 
thermometer controlled by shelters and by protective cover- 
ing. (c) The importance of disease as a factor has been rec- 
ognized by the great development of the subject of plant 
pathology. 
3. The third agricultural process is the harvesting of crops, 
in which ecology does not function very largely, except in so 
far as it may assist in the determining of the time of maximum 
returns, 
C. Nature of Contributions of Ecology. Agriculture, as 
its name implies, is a practical process and its methods hereto- 
fore have been largely empirical. This may be observed by 
reference to any agricultural textbook or farmer’s bulletin, 
where frequently processes are referred to as having been 
tested in certain localities and are recommended as having 
succeeded, or are condemned as failing. Even in our more 
recent Experiment Station work, the same tendency is shown 
in the accumulation of masses of data with too little correla- 
tion and generalization. The purpose of experimentation is 
to determine causes and draw general principles whose appli- 
cation will avoid the necessity of further experiments. Failure 
to generalize nullifies this purpose; in fact, unlimited experi- 
mentation is empiricism. 
On the other hand, the ecological method is scientific, in- 
volving interpreting as well as observation. Its materials are 
largely the same as those of agriculture, and when its methods 
are applied to these materials, we have the only result that 
can truly be called “the science of agriculture.”’ In so far as 
agriculture uses scientific methods, it is ecology. 
D. Illustrations from Definite Contributions of Ecology. 
Atmospheric moisture is observed quantitatively by means 
of the atmometer, which may be used as a measure of plant 
transpiration. Recent results show a most remarkable detailed 
correspondence between the curve of an open pan atmometer 
and that of a controlled plant of alfalfa. In soil moisture 
content the mechanical determining of the wilting coefficient 
by the centrifugal method is a valuable achievement, and is 
having an increasing application in the determining of the 
quantity of water to be applied in irrigation. The study of 
