PART II 



PRINCIPLES OF BIOLOGY ILLUSTRATED BY 

 TYPES OF PLANTS* 



PART I has given an introduction to many of the general 

 facts and principles concerning animals and plants. It has 

 been possible to do this by studies of one animal and one plant, 

 because in a general way there is great similarity among 

 living things. But the introductory study will lose much of 

 its value as useful science unless the reader goes on to study 

 illustrations and applications of the general principles. 

 Especially would one who had studied but two living things 

 have a very limited knowledge of the various forms of animal 

 and plant life, and of the many remarkable modifications of 

 structure of organisms which adapt them for carrying on the 

 life-processes in various ways. In order to extend our knowl- 

 edge of the principles of plant biology, we shall now make 

 a series of comparative studies of seed-plants or flowering- 

 plants, and later we shall study some of the most common 

 flowerless plants (moss, fern, mushroom, etc.). 



* To THE TEACHER : For possible changes in order of study of this and 

 later chapters see suggestions in the preface of this book and especially 

 Chapter VIII of the "Teachers' Manual of Biology," which accompanies 

 this book. 



145 



