xvi CONTENTS 



Page 



CHAPTER VIII 

 Water Relations of Plants 



64. General Concept of the Water Relations of Plants. The Amount 



of Water Used by Plants 278 



65. The Absorbing and Pumping Activity of the Root System. 

 Root Pressure, Guttation, and Bleeding of Plants 282 



66. Absorption of Water from the Soil. Water-holding Forces of the 

 Soil. Available and Unavailable Water 287 



67. Influence of Environmental Conditions on the Absorbing Activity 

 of the Root System. Methods of Studying the Absorption of 

 Water by Roots. Absorption of Water by Aerial Parts of the 

 Plant. . :\ 290 



68. Transpiration, Its Role in the Life of the Plant. Methods of 

 Studying Transpiration 294 



69. The Physiological Aspect of Transpiration. Its dependence on 

 Environmental Conditions and Its Daily Changes 301 



70. I^eaf Structure as a Factor in Transpiration. Stomatal and 

 Cuticular Transpiration 303 



71. Stomatal Apparatus of the Plant, Its Movements and Methods 



of Its Study. Nonstomatal Regulation of Transpiration 305 



72. Water Balance of Plants. The Phenomenon of Wilting and Its 

 Significance 311 



CHAPTER IX 



Translocation of Substances in the Plant 



73. General Concept of the Ascent and Descent of Water in the 

 Plant 320 



74. Osmotic Movement of Water 322 



75. Translocation of Water in the Vessels. Forces Causing Movement 



of Water; the Action of Transpiration 325 



76. The Rise of Water in the Trunk of a Tree. Cohesion of Water 



in the Vessels 328 



77. The Rate of Water Movement and the Resistance of Wood to 

 the Ascent of Water, Intermediate Motire Forces in the Trans- 

 location of water 334 



78. Translocation of Organic Substances in Plants and Their Storage . 337 



79. The Mechanism of Translocation of Organic Substances through 



the Plant. The Theory of Munch 339 



CHAPTER X 

 Resistance of Plants to Unfavorable Environmental 



Conditions 



80. Effect of Low Temperatures upon the Plant. Freezing of Plant 

 Tissues and Processes Accompanying It 350 



81. Frost Resistance of Plants. Hardening to Low Temperatures. 

 Methods for Determining Hardiness 352 



