xv i CONTENTS 



CHAPTER XII 



THE EFFECT OF WATER UPON GROWTH 



PA6B 



1. Efect 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. Hyphse 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 Stems 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 



