THE STAGE SETTING 



Fishing boats at the mouth of the Klamath River in northern Cahfornia. 

 Salmon run in on the outgoing tide apparently in response to the fresh water 

 coming out through the narrow mouth of the river. 



Chemical Factors 



Under this heading are inckided all of the chemical factors in the 

 environment of living things. Such are soil, rocks, and the various 

 salts and chemical substances found in food and water. Experi- 

 mental evidence shows that certain mineral substances are needed 

 for plant growth, and that these minerals are found in the composi- 

 tion of living matter. 



Alkali soils form a great problem of agriculture. In sixteen west- 

 ern states this is the greatest problem outside of the water supply. 

 In thirteen irrigated states there is enough alkali present to be harm- 

 ful to crops. Alkalies are chiefly harmful because their presence 

 causes the soil water to become permeated with these salts, thus 

 hindering absorption of water by the plant. 



Acidity of the soil is another problem for the agriculturist. It is 

 produced by a number of factors, such as the removal of calciinn from 

 the soil, or the production of acids by certain bacteria or from decom- 

 position. Acid affects the plant growth by checking the multii)lica- 

 tion of useful bacteria and keeps earthworms and other useful animalN 

 out of the soil. However, some species of plants demand aciti soils. 

 Mountain laurel, rhododendron, blueberries, and cranberries are 

 examples, as are sphagnum mosses found in certain bogs. 



