XX CONTENTS. 



PAGE 



Emission of the Pollen-tube 429 



Time required for the Descent of the Pollen-tube 431 



The Ovule 432 



Structure and Development 432 



Changes following Fertilization 435 



FERTILIZATION IN GYMNOSPERMS 437 



The Pollen-grain ,437 



The Ovule 43e 



Contact of the Pollen with the Ovuls 438 



Contrast between the Results of Sexual and Non-sexual Reproduction 443 



Bud-propagation . . . . 444 



Apogamy 446 



Parthenogenesis 446 



Polyembryony 446 



Close and Cross Fertilization 447 



Nectar ....... ...... 451 



Secreting glands . 451 



Specific Gravity 452 



Period of most Copious Secretion 452 



Colors of Flowers ., 452 



Odors of Flowers '.%....'.... 454 



Hybridization 455 



CHAPTER XV. 



THE SEED AND ITS GERMINATION. 



Nature of the Life of the Embryo . 459 



Ripening of Fruits and Seeds 460 



Dissemination of Seeds 460 



Vitality of Seeds 461 



GERMINATION 462 



Conditions of Germination 462 



Moisture 462 



Access of Free Oxygen 464 



Temperature 464 



Phenomena of Germination . . . . 466 



Fire-weeds . 469 



CHAPTER XVI. 



RESISTANCE OF PLANTS TO UNTOWARD INFLUENCES. 



Extremes of Heat and Cold 470 



Winterkilling 472 



Intense Light 473 



Improper Food 473 



