304 THE HOME GARDEN 



outer portions of the roots of most plants are provided with 

 these little structures, so that water is constantly being taken 

 by absorption. Since plants pass off many times their own 

 weight of water by evaporation through their leaves during 

 the growing season, the root hairs must have a very con- 

 siderable work to do. We shall not try to show now how 

 they take the water in. It is sufficient to know that water 

 with its soluble mineral salts passes from these root hairs 

 up through the roots and stems to the leaves where, as we 

 shall see, it is used in making living matter and food for 

 the plant. 



The root hairs take more than water out of the soil. 

 If a root possessing root hairs is washed carefully, it will be 

 found to have little particles of soil still clinging to it. These 

 particles of soil seem to be cemented to the sticky surface 

 of the root hair. Root hairs give off an acid. Sometimes 

 soils become too acid. Lime added to such soils helps to 

 neutralize the acid and make them fit for garden use. Acids 

 in the soil help dissolve some of the mineral substances. 

 The resulting solutions mixed with soil water are absorbed 

 by the root hairs. There is also much mineral matter 

 from the soil dissolved in water without the aid of the 

 acid, which is taken up by the root hairs. 



Plants take nitrogen from the soil. One very neces- 

 sary element in the composition of living matter is nitro- 

 gen. Nitrogen makes up nearly four fifths of the air 

 around us, and yet it is not available for use by plants 

 until certain bacteria In the soil have acted on it. Some 

 of these bacteria live in little nodules or lumps on the 

 roots of clovers, peas, beans, and other plants called le- 

 gumes and have the power in some mysterious way to take 

 some of this nitrogen out of the air and fix it so that it 



