GENERAL PAPERS 127 
culture (in its special sense), which includes 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 the subjects of sylviculture, mensuration, 
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 processes and principles are in the main the 
same, being varied in practice for the different ends. 
B. Agricultural processes with their ecological significance. 
1. The preparation of optimum conditions. The prepara- 
tion of the soil is the first condition, but as the principles are 
the same as those in the preservation of optimum conditions, 
it will be considered under that heading, The second import- 
ant factor is the securing of suitable stock, either seed or vege- 
tative, for which the criteria are the taxonomic relations and 
the reactions to the environment. The choosing of this stock 
is a question of balancing specific reactions of the desired plant 
with the factors of the necessary location, or vice versa, The 
securing of this stock is brought about either through breed- 
ing by pollination, or by grafting; and by choice, through the 
testing of known varieties, the selecting of the results of breed- 
ing, or the discovery of new varieties. Of course through all 
these methods runs the question of reaction to the desired en- 
vironment. A third ecological factor in preparation of con- 
ditions consists in the choice of a suitable time and location 
for the culture. 
2. The preservation of optimum conditions. (a) The con- 
dition of first importance is the soil. In its moisture content 
the maintenance of optimum moisture conditions is of course 
extremely important. The maintenance of its physical con- 
dition is popularly called tillage. The chemical composition 
is shown by analysis and experiments with plants, and is 
modified by the use of fertilizers and of other chemicals. The 
temperature of the soil is less considered, but may be deter- 
mined by the use of soil thermometers. (b) Optimum condi- 
tions of light, wind, and temperature depend 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 effect of wind is shown largely 
