SUMMARY OF CONTENTS xiii 



2. la plagiotropic organs. Radial organs, 446 ; rhizomes and lateral roots, 

 446 ; disposition due to internal influences, 447 ; autotropism, 448 ; branches 

 of trees, 449 ; disposition due to external influences, 450. Dorsiventral 

 organs, 452; branches, 452; flowers, 452; leaves with nutation and 

 variation movements, 453, Twining plants, 455; revolving movements, 

 456 ; twining, 458. 



b. Heliotropism. Likeness to geotropism, 460. 



1 . In orthotropic organs. Positive heUotropism, 460 ; disposition to negative 



hehotropism, 462 ; significance of hght intensity, 462 ; adaptibility to Ught, 

 463. Behaviour in nature, 464. 



2. In plagiotropic organs. Leaves. Growth movements, 464; variation 



movements, 466 ; fixed light position, 466. Other organs, 467. 



3. Precedent phenomena in stimulation. Separation of zones of perception 



and reaction. Grasses, 468 ; Malvaceae, 470 ; roots, 470. Precedent 

 phenomena in perception, 471 ; direction or intensity of light, 471 ; liminal 

 intensity, 473 : latent period, 473 ; quaUty of hght, 474 ; immediate cause 

 of phototropic activity, 474. Other phenomena in the chain of stimula- 

 tion, 474. 



c. Combined action of geotropism and heliotropism, 476. 



d. Other tropisms, 478. 



1. Thermotropism, 478. 



2. Electrotropism and galvanotropism, 480. 



3. Chemotropism, 481 ; aerotropism, 484 ; hydrotropism, 485 ; orientation with 



reference to the substratum, 486, 



4. Traumatotropism, 486. 



5. Rheotropism, 486. 



B. Nastic Curvatures (Bending Movements) 



a. Haptotropism (transition from tropisms to nastic curvatures). 



1. Tendrils, 487. Result of temporary contact. Tendrils which are sensitive on 



one or on all sides, 490 ; more exact estimate of contact stimulus, 490 ; 

 other stimuU, 492 ; curvature, 492. Encircling of the support ; produc- 

 tion of continuous twining, 494 ; further results, 494. 



2. Leaf tendrils, climbing roots, Cuscuta, 495. 



3. Drosera, 496. Character of the movement induced, 496. Stimuli and reac- 



tions, 497 ; direct stimulation, 497 ; indirect stimuh, 498. 



4. Heat stimuU in haptotropic organs, 499. 



b. Nyctitropism. 



1. Paratonic movements, 501. Growth movements; flowers which react to 



changes in temperature (501) and in Ught (502); foliage leaves, 503. 

 Variation movements, 503 ; mechanics, 505 ; influence of gravity, 506. 



2. Periodic movements, 508 ; movements due to after-efi^ects, 508 ; genesis of 



periodicity, 509; mechanics of periodic movements, 510. 



c. Shock movements. 



1 . Mimosa, 512; character and significance of the movement, 513; preliminary 



changes in the articulation, 514; recurrence of the capacity for reaction, 

 515; estimation of the shock stimulus, 516; other stimuli, 516; trans- 

 mission of the stimulus, 517. 



2. Stamens of Cynareae, 519. 



3. Other examples, 520. 



C. Review of Paratonic Movements 



Influence of external conditions on movements. Stimuli, 522. Releasing stimuli in 

 mechanisms and organisms, 522; perception and reaction, 522; formal con- 

 ditions, 526 ; general, 526 ; nature of their action, 527. 



