x Contents 



PAGES 



and water-holding capacity Exceptional plants Unavail- 

 able water - - Leaves poorly fitted for water absorption 

 Laboratory work References ..... 35-63 



CHAPTER IV 



CONDITIONS AND PRINCIPLES OF ABSORPTION 



Imbibition phenomena Osmosis and diffusion The demon- 

 stration of osmotic pressure An explanation of osmotic 

 pressure Plasrnolysis and wilting Variation in turgor 

 Substances active in producing turgor Osmosis and the 

 absorption of nutrient salts Protoplasmic permeability 

 The r61e of diffusion and osmotic pressure Sap or root 

 pressure Laboratory work References . . . 64-83 



CHAPTER V 



TRANSPIRATION AND WATER MOVEMENT 



Observations upon transpiration Amount of transpiration 

 The mechanism permitting transpiration Distribution of 

 stomata The control of water-loss by stomatal movement 

 - Modifications tending to check excessive transpiration 

 Conditions affecting transpiration - - Effects of excessive 

 evaporation Guttation- -Transpiration and evaporation 

 Transpiration and growth - - Water transport - - Fibrovas- 

 cular bundles Leaf venation -- Rate of transport Labora- 

 tory work -- References ...... 84-115 



CHAPTER VI 



THE WATER REQUIREMENTS OF CROPS AND OF VEGETATION 



Relative requirements of a few crops Precipitation and crop 

 growth - - Irrigation - - Potted plants and water-supply 

 Ecological classification based upon the water relation 

 Semi-xerophytism and hard-wheat production Subsidiary 

 work References . 116-135 



