CONTENTS xi 

 CHAPTEE XV. 



VXiiVi 



Special Sensitiveness and its Results . . 492 



Heliotropism . . . . . . 493 



Geotropism . . 494 



Contact .... . . . . 49o 



Chemical stimuli . ... 499 



CHAPTER XVI. 



The Nervous Mechanism op Plants . . . 500 



CHAPTER XVn. 



Automatism — Rhithh . . . , 506 



Automatic movements ... ... 507 



Ciliary motion .... . 507 



Creeping movements of Myxoraycetes . 507 



Contractile vacuoles . 508 



Rotation of protoplasm ... . . 508 



Rhythmic movements . 509 



Periodicity . . 510 



Artificial rhythm . . . 511 



CHAPTER XVIII. 



Repkoduction . . 512 



Vegetative reproduction ..... . 512 



Asexual reproduction by spores or gonidia . . 5l:-i 



Sexual reproduction by gametes . . . 514 



Alternation of generations .... 514 



Evolution of sexuality ... . . . 515 



Fertilisation ... . . 517 



Pollination ...... ... 518 



Dichogamy . ... 519 



Diolinism . . . .... 520 



Dimorphism and Trimorphism . . . 520 



Prepotency . . . 521 



Cleistogamy ... . .521 



Hybridisation . . 521 



Germination of seeds . . . 522 



Apospory, apogamy, and parthenogenesis ... . .52,S 



