INTRODUCTION 3 



plants. They act as natural scavengers, getting rid of 

 all kinds of dead organic matter through the process of 

 fermentation and decay which they initiate and maintain. 

 Several industries, such as the manufacture of butter and 

 cheese, could not flourish without their aid. On the 

 whole their action is beneficial. Certain kinds are 



FIG. 2. Drop of hay infusion, a. Protozoon ; l> hypha of a fungus ; 

 c spores of fungus ; d and e bacteria. (700). 



however, the cause of some of the most fatal diseases 

 affecting man and the lower animals. 



3. Relationship of these Organisms to others in the 

 Vegetable Kingdom. As bacteria are generally spoken 

 of as minute unicellular plants, it is of interest to indicate 

 the position in which they are usually placed among the 

 divisions of the Vegetable Kingdom, 



