CONTENTS. 



IX 



LECTURE XV. 



GROWTH 



1. The Mechanics of Growth, 334 



2. Structure and Properties of Growing Organs, 338 



3. Tensions in Growing Organs, 342 



4. Influence of the Tensions upon the Growth of the 



Cells, 348 



5. The Grand Period of Growth in Length, 354 



6. Nutation, 359 



PAGE 

 331370 



LECTURE XVI. 



IRRITABILITY . .- . . 371415 



i. The Irritability of Growing Organs, 375 



Temperature, 376 



Light, 379 



The Daily Period of Growth in Length, 400 

 Daily Periodicity of the Tensions of the Tissues, 405 



Gravitation, 409 



Electricity, 410 



Pressure and Traction, 410 



LECTURE XVII. 

 IRRITABILITY OF GROWING ORGANS (continued} 



Radiant Energy. Heliotropism, 

 ,, ,, Thermotropism, 



427 

 434 



416453 



LECTURE XVIII. 

 IRRITABILITY OF GROWING ORGANS (continued} 



Gravity. Geotropism, 

 Current of Water. Rheotropism, 

 Galvanic Current. Galvanotropism, 

 Substratum. Somatotropism, , 

 Moisture. Hydrotropism, 



454 

 473 

 474 

 4/4 

 477 



454483 



LECTURE XIX. 

 IRRITABILITY OF GROWING ORGANS (continued] 



Contact, 

 Combined Effects, 



484 

 496 



484518 



LECTURE XX. 



IRRITABILITY (continued] . *. . . 

 i. The Irritability of Mature Organs, 



519 



519556 



