84 SOILS AND PLANT LIFE 



In the dicotyledon, the bean, you will see that the first 

 root is a permanent one and grows downward rather deep 

 into the soil. Bear in mind these characteristic root habits 

 when you come to study the cereals and legumes. The 

 roots of the clovers and alfalfa penetrate deep into the 

 subsoil, bringing up plant food which is left near the sur- 

 face when these crops are plowed under. The shallow- 

 rooted cereals and grasses which follow them are thus 

 benefited. 



Draw in your notebooks the root systems of the corn 

 and the bean. 



60. How Roots help dissolve Mineral Matter. — In 



Section 7 we learned that certain mineral elements are 

 essential to the growth of any plant. These elements 

 are found in the soil, and it is a part of the work of roots, 

 by the excretion of acids, to help dissolve them. 



EXERCISE 28 



Object. — To show that roots give out, as well as take in. 



Procedure. — Fill a small bottle almost full of water, 

 and add a few drops of ammonia water, or dissolve in it a 

 grain or two of ordinary lye. Drop a slip of pink litmus 

 paper into it, and its color will begin to change. In a 

 short time it will have become blue. This shows that the 

 solution is alkaline, for alkalies turn pink or red litmus 

 paper blue. 



Now add a little acid of any kind, — vinegar will do, — 

 and presently the slip of blue paper will begin to change in 

 color again, turning this time from blue to red. Finally, 

 its color will be about the same as it was at the beginning. 

 This shows that the solution is now acid, for acids turn 

 blue litmus paper red. We are able by this test to tell 

 whether any solution is acid or alkaline. 



