BOTANY 



PART I.— PLANT RELATIONS 



CHAPTEE I. 



INTRODUCTION. 



1. General relations. — Plants form the natural covering 

 of the earth's surface. So generally is this true that a land 

 surface "\vitliout plants seems remarkable. Xot only do 

 plants cover the land, but they abound in waters as well, 

 both fresh and salt waters. They are wonderfully varied in 

 size, ranging from huge trees to forms so minute that the 

 microscope must be used to discover them. They are also 

 exceedingly variable in form, as may be seen by comparing 

 trees, lilies, ferns, mosses, mushrooms, lichens, and the 

 green thready growths {algcB) found in water. 



2. Plant societies. — One of the most noticeable facts in 

 reference to plants is that they do not form a monotonous 

 covering for the earth's surface, but that there are forests in 

 one place, thickets in another, meadows in another, swamp 

 growths in another, etc. In this way the general appear- 

 ance of vegetation is exceedingly varied, and each appear- 

 ance tells of certain conditions of living. These groups of 

 plants living together in similar conditions, as trees and 

 other plants in a forest, or grasses and other plants in a 

 meadow, are known a.i plant societies. These societies are as 



