62 AGRICULTURE. 



that the amounts of water evaporated from 

 the soil and given to the air ahiiost 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 di'-y 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. 



[F) Weigh the plant accurately, and record the 

 weights. 



(r) Hang the plant in a warm, dry place for two or 

 three weeks, or until perfectly dry. 



{ci) Weigh again, and record weights. What per cent, 

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



4. Tends to Regulate Tempei^ature. — 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- 



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

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



{U) 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? 



