xii CONTENTS 



minate method of growth; the seed and the embryo; general organi- 

 zation of the plant. 



X. Roots and Their Functions 142 



The structure and functioning of roots; intake of water and dissolved 

 substances. 



XI. Stems and Their Functions 152 



The structure and functioning of stems; the vascular tissues and 

 transport of materials within the plant. 



XII. The Leaf and Its Functions ICG 



The structure and functioning of the leaf; the manufacture of food by 

 photosynthesis; some further aspects of plant physiology. 



C. The Varied Patterns of Individual Organization 



XIII. Some Other Types of Individual Organization: Variety of 



Structure Versus Uniformity of Function 177 



The varied patterns of animal life; structural levels; different ways 

 of doing the same things. The major patterns of plant life; types of 

 organization among the green plants; plants which lack chlorophyll. 



PART II. THE CONTINUITY OF THE RACE 



A. Reproduction 



XIV. The Individual as a Member of a Race 207 



The discarded theory of spontaneous generation ; all life comes from 

 life. 



XV. The Reproduction of Animals 211 



Reproduction in the Protozoa. Reproduction in the Metazoa; germ 

 and soma; asexual and sexual reproduction; maturation of the germ 

 cells and fertilization of the egg; parthenogenesis; breeding habits 

 in the Metazoa; embryonic development. 



XVI. Human Reproduction 241 



The male and female reproductive systems; sex hormones and the 

 female reproductive cycles; human embryology. 



XVII. Reproduction in Plants 254 



The alternation of generations; reproduction in the thallophytes, 

 bryophytes, pteridophytes, and spermatophytes. 



B. Inheritance and Variation 



XVIII. Mendel's Laws of Inheritance 277 



The discovery of Mendelian inheritance; the monohybrid cross and 

 Mendel's first law; the dihybrid cross and independent assortment or 

 Mendel's second law; the trihybrid cross. 



