THE FLOWER GARDEN 309 



and this makes it necessary to keep the soil 

 properly supplied with moisture. 



The presence of the proper chemical elements 

 and moisture, however, is not the only thing that 

 is needed for the root hairs to do their work well. 

 Air must be present in the soil or it will be im- 

 possible for the root hairs to secure the necessarj' 

 food for the plant. 



The air in the soil must mostly come from the 

 surface so it is obvious that it is always necessary 

 to keep the surface of the ground in such a condi- 

 tion that it will admit air. Thorough cultivation 

 and deep plowing keep the soil in a loose 

 condition. 



Knowing that the plant's roots must have 

 plenty of air, one enjoys stirring the soil deeply 

 for he knows that by this method the crop will be 

 increased. 



Cultivation must be frequent because the sur- 

 face of many soils has a tendency to become 

 rather hard and compact, especially after heavy 

 rains. 



We may consider that there are minute tubes 

 leading from the surface down into the soil. 

 AVTien the tops of these tubes are closed by hav- 

 ing the soil bake it is easy to see that the supply 

 of air is cut off. Stirring the surface, then, 

 makes a connection with the outside air. 



