CHAPTER LI. 

 BIOLOGY. PART I . BOTANY. 



PLANTS AND ANIMALSS TRUCTURE OF PLANTS FLOWERING PLANTS 

 THE STEM THE LEAVES FORMS OF LEAVES. 



BIOLOGY is derived from the Greek word Bios, " life," and logein, " to speak," 

 and constitutes the science of ORGANIC LIFE. This science is divided into 

 two branches : BOTANY, relating to the life of plants ; ZOOLOGY, to the 

 animals. 



Plants, then, are living things, and as we proceed we shall find them 

 born, or "germinating," growing up as young plants, maturing as adults, 

 finally dying, and their particles resolving into their elements. There 



is more than one application of 

 the text, " Man is but as a flower 

 of the field." 



In the GEOLOGICAL section 

 we noticed the progressive stages 

 of the vegetable creation, and if 

 we turn back to those pages 

 wherein the various epochs of 

 the earth's formation are enu- 

 merated, we shall see how plant- 

 life developed. Thus we find in 

 the Cambrian the first traces of 

 vegetable life in the weeds of 

 primeval seas. The Silurian 

 strata and the Devonian furnish 

 us with many fossils of marine 

 algae, and if we examine the suc- 

 ceeding periods we shall find a 

 progressive increase and develop- 

 ment ; pines and tree-ferns in the sandstone, and most of the plants (by 

 which term we include all varieties) were different from those at present 

 existing in the earth. 



We spoke of climate lately, and referred to the vegetation having an 

 influence upon it. The same is true of the effect of climate upon vegeta- 

 tion. The conditions of plant-life depend upon climate, as it partly depends 



I'ig. 735. Branch of the oak. 



