ELEMENTARY BOTANV 



CHAPTER I. 



INTRODUCTORY— DEFINITION AND SCOPE OF THE 

 SCIENCE. 



Botany is the science which deals with those special forms of 

 living organisms known as Plants. This at once raises the 

 question — What do we mean by a plant ? The higher forms 

 of animal and vegetable life can be easily distinguished the one 

 from the other ; but when we descend to the lower forms we 

 find it most difficult, if not impossible, to draw a line of de- 

 marcation between them. 



The old distinction between the three kingdoms of nature 

 was a simple one : minerals grow — plants live and grow — 

 animals move, live, and grow. Putting aside for the moment 

 the question as to whether minerals really grow, the phenomena 

 of motion cannot be accepted as defining the difference between 

 the two groups of living beings. Many plants, especially 

 amongst the lower forms, are capable of motion at some time 

 or other during their life. As an example, if we examine rain- 

 water that has been standing for some days, we generally find 

 minute green masses floating about in it. These on inspection 

 under a microscope prove to be true plants {Protococciis pluvi- 

 alis), each being a little rounded mass containing green particles. 

 After watching for some time, however, it will be seen that 

 some of these plants change their form, becoming more pear- 

 shaped, at the same time giving off two very minute threads or 

 cilia. These are thrown into rapid motion, propelling the plant 



B 



