42 GROWTH AND WORK OF PLANTS 



reaching down to the ground water below. The spaces between 

 the soil particles are filled with air, which is very necessary for 

 the health of the plant. The root hairs of plants being attached 

 very closely and firmly to some of these soil particles are thus 

 brought into very close contact with the water film in the soil, 

 and absorb it, while fresh water is drawn through the film from 

 the ground water below. Where free soil water is present in the 

 soil for any length of time about the roots of most dry land plants, 

 the plants become sickly. Many plants, however, grow in soil 

 where there is free soil water continually, or for a great portion 

 of the time. Examples are seen in the swamp plants, semia- 

 quatics, etc. 



