September 7, 1917] 



SCIENCE 



227 



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. 

 — It is admitted by all, that agriculture is 

 largely an art, and that its processes until 

 rather recently were developed almost en- 

 tirely by empirical methods. Evidences of 

 this are still shown in many agricultural 

 texts and farmers' bulletins, where proc- 

 esses are recommended because of success in 

 certain localities or condemned because of 

 failure. 



As scientific knowledge and methods ad- 

 vanced, the agriculturists began to take ad- 

 vantage of these methods and we find many 

 agricultural practises based on truly scien- 

 tific work. This is especially true of the 

 agricultural chemists from the days of Lie- 

 big down, although their claim to the title 

 agriculturalists in the ordinary sense of the 

 word might be questioned by some. 



It must be recognized that many of the 

 methods of agriculture are still empirical, 

 and in some cases necessarily so on account 

 of the lack of equipment of the constit- 

 uency, but it is admitted that the scientific 

 are better where possible. Even in experi- 

 ment station work, there is a danger pres- 

 ent, through the tendency to accumulate 

 masses of data with too little correlation 

 and generalization. The purpose of experi- 

 mentation is to determine causes and to 

 draw general principles whose application 

 will avoid the necessity of further experi- 

 ments. Failure to generalize nullifies this 

 purpose; in fact, unlimited experimenta- 

 tion is empiricism. 



The methods of ecology are scientific, its 

 materials are largely the same as those of 

 agriculture and its practical applications 

 are found chiefly in the field of agriculture. 

 For these reasons it is evident that ecology 

 belongs both to botanj^ and to agriculture. 



and in fact covers the debatable ground be- 

 tween the two subjects. Instead of this 

 being, as is too often the case under such 

 circumstances, the cause of rivalry and 

 even conflict, it should furnish a common 

 ground for cooperation and both parties 

 should endeavor to maintain a high stand- 

 ard in investigation and generalization of 

 the condition of plant responses to environ- 

 mental factors. 



The services of ecology to agriculture 

 then are twofold, first in the developing of 

 the principles on which agricultural prac- 

 tices are to be based, and second in furnish- 

 ing a comprehensive source of information 

 for the handling of specific eases and the 

 answering of specific questions of agricul- 

 tural policy. 



D. Illustrations from Definite Contrihu- 

 tions of Ecology. — Atmospheric moisture is 

 observed quantitatively by means of the 

 atmometer, which may be used as a meas- 

 ure of plant transpiration. Eecent results 

 show a most remarkable detailed corre- 

 spondence 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 in- 

 creasing application in the determining of 

 the quantity of water to be applied in irri- 

 gation. The study of the extension of root 

 systems is having an increasing influence 

 in determining the relation of plants to the 

 soil moisture content. 



In light we have both the measure of the 

 intensity of light by Wiesner and Clements, 

 and recently the measurement of photolytic 

 ability of light by a delicate apparatus de- 

 vised by MacDoiigal. Under chemical con- 

 tent the recent work of Coville with blue- 

 berries is widely known on account of its 

 publication in the National Geographic 

 magazine. One of the difficulties of this 



