226 



SCIENCE 



[N. S. Vol. XLVI. No. 1184 



economic importance under the special sub- 

 ject of bacteriology, mycology, etc. 



n. RELATION OF ECOLOGY TO AGEICULTUEE 



A. Purpose and Scope of Agriculture. — 

 The subject of agriculture is extremely 

 complex and even the terminology is not 

 uniform in usage. Even the word agricul- 

 ture itself is employed in a general and a 

 special manner. It is used here in the gen- 

 eral sense of the cultivation of plant prod- 

 ucts from the soil. Its complexity is made 

 evident by consideration of the varied ends 

 sought, which include size, strength, water 

 content, and chemical contents of stem, 

 leaves, roots, flowers, fruit and special 

 parts such as fibers, cork, etc. 



The resulting subdivisions of the subject 

 following largely the usage of Bailey's 

 ' ' Cyclopedia of Horticulture, ' ' are : Agri- 

 culture (in its special sense), which in- 

 cludes the culture of grain, forage crops, 

 bread stuffs, textiles, etc.; horticulture, 

 which includes fruits, vegetables, flowers 

 and ornamental plants ; and forestry, which 

 is the complete treatment of other trees, 

 and includes subjects of sylviculture, men- 

 suration and harvesting. Through all this 

 complexity runs a general unity of purpose, 

 namely, the preparing and maintaining of 

 optimum conditions for the production of 

 maximum returns. Therefore the proc- 

 esses and principles are in the main the 

 same, being varied in practise for the dif- 

 ferent ends. 



B. Agricultural Processes with their 

 ecological significance. 



1. The preparation of optimum condi- 

 tions. The preparation of the soil is the 

 first condition, but as the principles are the 

 same as those in the preservation of opti- 

 mum conditions it will be considered under 

 that heading. The second important fac- 

 tor is the securing of suitable stock, either 



seed or vegetative, for which the criteria 

 are the taxonomic relations and the reac- 

 tions to the environment. The choosing of 

 this stock is a question of balancing specific 

 reactions of the desired plant with the fac- 

 tors of the necessary location, or vice versa. 

 The securing of this stock is brought about 

 either through breeding, by pollination, or 

 by grafting; and by choice, through the 

 testing of known varieties, the selecting of 

 the results of breeding, or the discovery of 

 new varieties. Of course through all these 

 methods runs the question of reaction to 

 the desired environment. A third ecolog- 

 ical factor in preparation of conditions con- 

 sists in the choice of a suitable time and lo- 

 cation for the culture. 



2. The preservation of optimum condi- 

 tions, (a) The condition of first impor- 

 tance is the soil. In its moisture content the 

 maintenance of optimum moisture condi- 

 tions is of course extremely important. The 

 maintenance of its physical condition is 

 popularly called tillage. The chemical com- 

 position is shown by analysis and experi- 

 ments with plants, and is modified by the 

 use of fertilizers and of other chemicals. 

 The temperature of the soil is less consid- 

 ered, but may be determined by the use of 

 soil thermometers. (&) Optimum condi- 

 tions of light, wind and temperature de- 

 pend upon exposure, and may be controlled 

 by modifications of this exposure. Light is 

 studied by light intensity experiments and 

 controlled by screening or by thinning. 

 The efliect of wind is shown largely by 

 transpiration, measured by the atmometer, 

 controlled by thinning or by windbreaks. 

 Temperature is observed by the thermom- 

 eter and controlled by shelters and by pro- 

 tective covering, (c) The importance of 

 disease as a factor has been recognized by 

 the great development of the subject of 

 plant pathology. 



3. The third agricultural process is the 



