THE OFFICES OF THE PLANT 111 



loose sands from drifting by winds, as along the coasts of the 

 sea. Sand- loving plants with strong running roots or root- 

 stocks as various grasses and sedges are used for this pur- 

 pose. One of the uses of windbreaks is to lessen the drifting 

 of sands. Bluffs and railway embankments are often held from 

 caving and washing by means of strong-rooted plants. 



172rt. Large forests probably have some influence in dis- 

 tributing the rainfall, the precipitation tending to be greatest 

 near the forest areas. By some persons it is thought that the 

 total precipitation is increased by forests, but this point is in 

 dispute. The off-flow or outflow from forest-covered, or from 

 any plant-covered, lands is more gradual than from bare lands ; 

 thus floods are more frequent and more serious the more com- 

 pletely the forests are removed. This is illustrated in the floods 

 on the Ohio and other rivers. 



1726. Plants lessen evaporation chiefly in the capacity of 

 shelter-belts. Windbreaks check evaporation from adjacent lands 

 (see King, "The Soil," pp. 204-206); and this is one valuable 

 effect of windbreaks for fruit-plantations in dry climates (see 

 Bailey, "Principles of Fruit -Growing," pp. 48 51.) Forest areas 

 contribute some of their moisture to the atmosphere of con- 

 tiguous areas ; and plants give off moisture from their grow- 

 ing parts. 



173a. For a full discussion of windbreaks, see "Principles 

 of Fruit-Growing," pp. 47-57, 62-92. 



