BOTA^^Y 



PLANT STUDIES 



CHAPTER I 



INTRODUCTION 



1. General relations. — Plants form the natural corerinff 

 of tlie eurtli's surface. So generally is this true that a land 

 surface without plants seems remarkable. Xot onlv 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 liy comparing 

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

 green thready growths (algw) found in water. 



2. Plant societies. — One of tlie most noticealilo 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 as plant societies. These societies are as 



1 



