BY IRRIGATION. 263 



effect of water, at such a period, is to dilute the sap and to 

 furnish the means of transpiration ; for all the excess of wa- 

 ter, taken up by the roots, is thrown off by the leaves. 

 Hence the quantity transpired depends upon that imbibed. 



2. During the rest of plants in the winter of northern cli- 

 mates, and the dry season under the tropics, but a small 

 quantity of water is required, because the plants do not trans- 

 pire it. Excess of moisture at such seasons, often distends 

 the vessels and exposes them to injury by the frosts of spring. 

 No more water should be supplied than is taken up by the 

 capillary attraction of the soil. 



3. It is during the growth of plants, and when their leaves 

 are fully matured, that the greatest quantity of water is re- 

 quired. The young leaf tranpsires much more in proportion 

 to its surface than when fully matured, and hence requires a 

 greater quantity to be absorbed by the roots ; but when the 

 leaves grow old, their cuticle hardens, and the apertures 

 through which the water passes off, gradually become closed 

 up ; hence, water should be supplied to plants abundantly 

 when they first begin to grow, and should be diminished as 

 they grow older. During the ripening of the succulent fruit, 

 plants require the least quantity ; and if a large amount is 

 supplied at that season, the fruit may be plumper, but will 

 loose much in quality. Strawberries niay be increased in 

 size, by flooding their beds with water during the period of 

 ripening, but they lose their flavor, and become insipid. 



It will be perceived, that this mode of improvement is of 

 limited extent unless in case of green houses and gardens. It 

 is applicable chiefly to light sandy soils. Heavy argillaceous 

 soils are never benefited by it. When dry soils are situated 

 in the vicinity of streams or Artesian wells, water may be 

 ^ brought on to them with highly beneficial effects. The char- 

 acter of the water for irrigation upon dry lands, is a point of 

 considerable importance. Water from a running stream is 

 vastly superior to that from wells or springs, and the farther 



