62 AGRICULTURE. 



that the amounts of water evaporated from 

 the soil and given to the air almost wholly 

 through the plant were : by barley and red 

 clover, 310 pounds of water to one pound of dry 

 matter produced; oats, 376 pounds; peas, 273 

 pounds ; and buckwheat, 363 pounds to one 

 pound of dry matter. Plants differ in their de- 

 mands for water, hence some kinds of plants are 

 found upon dry soils and others upon wet soils. 



3. Constitutes Plant-food. Water itself con- 

 stitutes an important plant food. 



EXPERIMENT 10. (a) Secure some green but well- 

 grown plant (roots and all), as clover, corn, or cow-peas; 

 carefully remove the soil from the roots. 



(^) Weigh the plant accurately, and record the 

 weights. 



(c] Hang the plant in a warm, dry place for two or 

 three weeks, or until perfectly dry. 



(</) Weigh again, and record weights. What per cent, 

 of the plant was water ? What per cent, dry matter ? 



4. Tends to Regulate Temperature. - - The 

 water which percolates through the soil from 

 spring rains is warmer than the soil and tends 

 to raise the temperature, while that from sum- 

 mer rains is cooler than the soil and tends to 

 lower the temperature. 



III. Field Exercise No. 3. 



(a) Let the student look for different kinds of soil as, 

 dry, sandy soil, and wet soil in the vicinity. 



() Note (observe and list) the kinds of wild or culti- 

 vated plants growing upon each kind of soil. Do some 

 plants thrive in one soil which are not found in others? 



