WATER A FOOD FOR PLANTS. 9 



depends upon some facts in vegetable physiology that are 

 not generally known or considered. These may be con- 

 densed into the following statement: 



Growing plants contain from 70 to 95 per cent of water. 

 To the extent that water supplies this necessary constitu- 

 ent of a growing plant, it is an actual nutriment. 



The solid portion of the plant consists of matters which 

 enter into it only while in solution in water. Water is 

 the vehicle by which the solid part of a plant is carried 

 into its circulation for assimilation. If water is not ade- 

 quately supplied, an insufficient quantity of nutriment 

 only will be carried into the circulation of the plant, and 

 its growth will be stunted or arrested altogether. 



No water, whether it be in the state of liquid or vapor, 

 can enter into any other part of a plant than its roots. 

 The common idea that water or watery vapor is ever ab. 

 sorbed through the leaves of a plant is unfounded. 



The quantity of water that must pass through the 

 roots of a plant of our ordinary farm crops, and to be 

 transpired through the leaves, to carry it from germina- 

 tion to maturity, is equal to a depth of 12 inches over the 

 whole soil covered by the crop. This is the requirement 

 of an average crop upon a moderately well-cultivated soil. 

 If the crop is stimulated to extraordinary growth by large 

 applications of manure or other fertilizers, a still greater 

 supply of water is needed to meet the demands of the 

 crop. Thus the yield of a crop depends in certain cases 

 entirely upon the amount of water supplied, and to a 

 certain extent bears an exact ratio with it. 



The summer rainfall in our climate is rarely, if ever, 

 adequate to the requirements of what would be a maxi- 

 mum crop, consistent with the possibilities of the soil. 

 Our intense heats cause a large proportion of the rain-fall 

 to be evaporated directly from the soiL Our copious 

 summer rains are seldom wholly retained by the soil, but 

 frequently in large part escape into streams and water- 



