xvi CONTENTS 



CHAPTER XII 

 THE EFFECT OF WATER UPON GROWTH 



PAOB 



1. Effect of Water upon the Rate and Quantity of Growth . . 350 



2. Effect of Water on the Direction of Growth Hydrotropism . 355 



1. Roots ' 356 



2. Rhizoids of Higher Cryptogams 357 



3. Stems . . 358 



4. Pollen-tubes 358 



5. Hyphae of Fungi 358 



Literature 360 



CHAPTER XIII 

 EFFECT OF THE DENSITY OF THE MEDIUM UPON GROWTH 



1. Effect of Density upon the Rate of Growth 362 



Literature 369 



CHAPTER XIV 

 EFFECT OF MOLAR AGENTS UPON GROWTH 



1. Effect of Molar Agents upon the Rate of Growth .... 370 



1. Contact 370 



2. Rough Movements 370 



3. Deformation 372 



4. Local Removal of Tissue ....... 375 



2. Effect of Contact upon the Direction of Growth Thigmotropism 376 



1. Twining Sterns 376 



2. Tendrils 377 



3. Roots 380 



4. Cryptogams 381 



5. Animals 382 



6. The Accumulation of Contact-stimulus and Acclimatization 



to it 382 



7. Explanation of Thigmotropism 383 



3. Effect of Wounding upon the Direction of Growth Trauma- 



tropism 384 



1. False Traumatropism 384 



2. True Traumatropism . . . . . . . 384 



4. Effect of Flowing Water upon the Direction of Growth Rheo- 



tropism 387 



Summary of the Chapter ......... 388 



Literature . 389 



