xx CONTENTS. 



PAGE 



Emission of the Pollen-tube 



Time required for the Descent of the Pollen-tube . . . i 



The Ovule 



Structure and Development 



Changes following Fertilization 



FERTILIZATION IN GYMNOSPERMS 



The Pollen-grain 



The Ovule 



Contact of the Pollen with the Ovule ; * 



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



Bud-propagation 4 



Apogamy 



Parthenogenesis 



Polyembryony ^ 



Close and Cross Fertilization 447 



Nectar 461 



Secreting glands 461 



Specific Gravity 462 



Period of most Copious Secretion 452 



Colors of Flowers 462 



Odors of Flowers 464 



Hybridization 465 



CHAFfER XV. 



THE SEED AND ITS GERMINATION. 



Nature of the Life of the Embryo 460 



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 . .... 412 



Intense Light 473 



Improper Food 



