CONTENTS xvii 



Page 



82. Other Harmful Effects during WintGring: Exhaustion, Drowning, 

 Heaving of Soil, Winter Desiccation. Physiological Basis of 

 Selection for Winter Resistance 358 



83. Effect of high temperatures on Plants. Heat Resistance 361 



84. Effect of Water Deficiency on the Plant. Soil and Atmospheric 

 Drought 363 



85. Peculiarities of the Water Balance in Dry Habitats. Xerophytes, 

 Mesophytes, and Hydrophytes 365 



86. Effect of Environment on the Structure of Transpiring Organs. 

 Xeromorphism and Drought Resistance 369 



87. Physiological Basis of Irrigation 374 



88. Injury to Plants from Excessive Humidity. Factors in the 

 Resistance of Bog Plants to Waterlogging. Lodging of Plants, Its 

 Causes and Means of Control 376 



89. Injury to Plants from Excess of Salts. Physiological Pecuharities 



of Halophytes. Alkah Resistance of Crop Plants 378 



90. Resistance of Plants to Fungi. Character of the Interrelations 

 between the Parasite and the Host. Immunity 382 



CHAPTER XI 



Interrelations between Different Parts of the Plant. 



Vegetative Propagation 



91. The Plant as a Unit Organism. Correlation 395 



92. Artificial Propagation of Plants by Cuttings and Layering. 

 Regeneration and Polarity. Root-forming Ho-rmones 398 



93. Grafts and Chimeras 403 



CHAPTER XII 

 Physiology of the Development of Plants 



94. Normal Cycle of Development of Higher Plants. Annual and 

 Perennial Plants. Interrelations between Growth and Develop- 

 ment 409 



95. Conditions for the Formation of Reproductive Organs. Hypoth- 

 esis of Klebs. Significance of Changes in the Chemical Com- 

 position of Plants 412 



96. Theory of Lysenko on the Stages in Development of Plants. 

 Yarovisation, Its Theoretical Foundation and Practical Signifi- 

 cance 416 



97. Influence of Length of Day on the Development of Plants. 

 Photoperiodism 422 



98. Physiological Differences between Winter and Spring Types, 

 Early and Late Plants. Basis of Selection for Earhness 428 



CHAPTER XIII 

 Physiological Processes during Flowering and Ripening 



OF Fruits and Seeds 



99. Physiological Processes during Blooming. Respiration of Flowers. 

 Nyctinastic and Seismonastic Movements 432 



