16 THE SOIL AND THE PLANT 



EXERCISES 



1. Make a collection of soils, classifying them in the various 

 groups to which they belong. 



2. Examine samples of soils with a low-power microscope 

 to detect, if possible, remnants of partially decomposed plants. 



3. Fill a glass tube 20 inches long and one inch in diame- 

 ter with air-dry sand, another with clay, and a third with loam, 

 after inserting a cotton plug in the lower end of each tube. 

 Now set these tubes in a pan of water and note the rapidity 

 with which the water rises in each tube. This upward move- 

 ment of water is due to capillarity. 



4. Fill one of the tubes used in the previous experiment 

 half full of sandy soil ; one, half full of clay soil ; and the last, 

 half full of loam. Now place in one a handful of coarse lumps, 

 in another a pinch of dry grass, and in the third some coarse 

 straw ; then fill each tube to the top with the sort of soil used 

 in the lower half. Set the tubes in the pan of water used in 

 the previous experiment. Does the water rise above the lumps, 

 grass, or straw? Why not? What does this teach about plow- 

 ing, disking, harrowing, and maintaining a soil mulch to pre- 

 vent evaporation ? 



5. Insert a glass tumbler over a small growing plant. Drops 

 of water soon appear on the inner surface of the glass. Where 

 does this water come from? What does it teach? 



HOME PROJECTS 



1. Make a collection of as many kinds of soil as can be found 

 on the home farm or in the neighborhood. 



2. Make a map of the home farm and show by means of 

 colors the distribution of the various kinds of soil found thereon. 



