MOVEMENT OF SOIL-MOISTURE 145 



diately destroys the conditions of equilibrium formerly 

 existing, for the moisture is not now uniformly dis- 

 tributed. Consequently a process of redistribution 

 begins which continues until the nearest approach 

 to equilibrium is restored. In this process water 

 will pass in every direction from the wet portion of 

 the soil to the drier ; it does not necessarily mean that 

 water will actually pass from the wet portion to the 

 drier portion; usually, at the driest point a httle 

 water is drawn from the adjoining point, which in 

 turn draws from the next, and that from the next, 

 until the redistribution is complete. The process 

 is very much like stuffing wool into a sack which 

 already is loosely filled. The new wool does not 

 reach the bottom of the sack, yet there is more wool 

 in the bottom than there was before. 



If a plant-root is actively feeding some distance 

 imder the soil surface, the reverse process occurs. 

 At the feeding point the root continually abstracts 

 water from the soil grains and thus makes the film 

 thinner in that locality. This causes a movement 

 of moisture similar to the one above described, from 

 the wetter portions of the soil to the portion being 

 dried out by the action of the plant-root. Soil many 

 feet or even rods distant may assist in supplying 

 such an active root with moisture. When the thou- 

 sands of tiny roots sent out by each plant are re- 

 called, it may well be understood what a confusion 

 of pulls and counter-pulls upon the soil-moisture 



