viii Contents 



PAGES 



Variations in the Amount of Water Used by Plants. Two 

 years compared Field and plant- house yields compared 

 Loss of water in a saturated air Amount of water 

 required to produce one ton of dry matter 39-46 



The Mechanism and Method of Transpiration in Plants. 

 Transpiration and breathing Structure of barley leaf 

 Inevitable loss of water by evaporation makes demands 

 large Amount of air breathed by clover to secure the 

 needed carbon Changes in humidity of air over a clover 

 field Assimilation of carbon takes place only in sun- 

 shine Breathing pores in leaves How stomata per- 

 mit and prevent loss of water Structure of breathing 

 pores 46-54 



Mechanism by which Land Plants Supplij Themselves with 

 Water. Part played by roots Essential features of 

 roots Only the newer portions active in . absorbing 

 moisture How water is taken up Rate of feeding 

 slows down as thickness of film becomes less Root 

 hairs acid and may hasten solution of plant-food Need 

 of great extent of root surface Distribution of roots in 

 soil How roots advance through soil The root-cap 54-65 



PART I 

 IRRIGATION CULTURE 



CHAPTER I 



THE EXTENT AND GEOGRAPHIC RANGE OF IRRIGATION 

 (pages 66-90) 



The Antiquity of Irrigation. In Egypt In Assyria By 

 the Phoenicians Early Grecian and Roman In China 

 In Mexico and Peru 66-72 



Extent of Irrigation. In the Po valley In Sicily In 

 Spain In France In Switzerland In Belgium In 

 Denmark In Austria-Hungaria In Bavaria In Eng- 

 land In India In Ceylon In Australia In other 



