CHAPTER I. 

 POSITION— RELATIONSHIPS. 



Bacteria are considered to belong to the plant kingdom 

 not because of any one character they possess, but because 

 they most nearly resemble organisms which are generally 

 recognized as plants. While it is not diflBcult to distinguish 

 between the higher plants and higher animals, it becomes 

 almost, if not quite, impossible to separate the lowest forms 

 of life. It is only by the method of resemblances above 

 mentioned that a decision is finally reached. It has even 

 been proposed to make a third class of organisms neither 

 plants nor animals but midway between in which the bac- 

 teria are included, but such a classification has not as yet 

 been adopted. 



In many respects the bacteria are most nearly related to 

 the lowest algcE, since both are unicellular organisms, both 

 reproduce by transverse division and the forms of the cell 

 are strikmgly similar. The bacteria differ in one important 

 respect, that is, they do not contain chlorophyl, the green 

 coloring matter which enables all plants possessing it to 

 absorb and break up carbon dioxide in the light, and hence 

 belong among the fungi. Bacteria average much smaller 

 than even the smallest algse. Bacteria are closely con- 

 nected with the fission yeasts and the yeasts and torulas. 

 All are unicellular and without chlorophyl. The bacteria, 

 as has been stated, reproduce by division but the others 

 characteristically by budding or gemmation, though the fission 

 yeasts also by division. 



There is a certain resemblance to the molds in their 

 absence of chlorophyl. But the molds grow as branching 

 threads and also have special fruiting organs for producing 

 spores as a means of reproduction, neither of which charac- 

 teristics is found among the true bacteria. The higher 



