12 AGRICULTURAL AND INDUSTRIAL BACTERIOLOGY 



eral, have the attributes of plant cells. They multiply by 

 transverse fission, while many of the protozoa multiply by 

 fission which is either longitudinal or at least not at right 

 angles to the longest axis of the cells. Bacteria are never 

 amoeboid in their movements as are protozoa of many types. 

 Furthermore, many intergrading forms exist between the 

 true bacteria and that group of plants known as the blue- 

 green algae. No careful student of bacterial morphology 

 can escape the conclusion that the relationships are prob- 

 ably closest to this group of plants, although a few of the 

 bacteria show close resemblances and relationships to cer- 

 tain of the mold fungi. 



Both from the standpoint of structure and of connecting 

 forms, the bacteria on the whole show closer relationship to 

 the plants than to the animals or protozoa. 



Confusion sometimes arises because of the fact that many 

 of the bacteria are actively motile. It should be recognized 

 that the ability to swim about is not a characteristic pe- 

 culiar either to plants or to animals. Many forms which 

 are definitely knovm to be plants possess this power, the 

 sperm cells, for example, of even some of the higher forms 

 of plants such as mosses, ferns and cycads, can move inde- 

 pendently.. A misunderstanding of this fact led to some 

 confusion in early studies of bacteria, for it is only within 

 the last half century that their true relationships have been 

 understood, and they have been placed definitely with the 

 plants. 



Position of Bacteria, Yeasts, and Molds in the Plant 

 Kingdom. — Botanists generally recognize four great sub- 

 divisions of plants, the seed plants or Spermatophyta, the 

 fern plants or Pteridophyta, the moss plants or Bryophyta, 

 and the thallus plants or Thallophyta. The bacteria, 

 yeasts, and molds all belong in this last group. 



The Thallophyta are separated from other plants in that 

 they do not develop a complex plant body with differenti- 



