252 GENERAL BOTANY 



found the nucleus in division, with spindles resembling those 

 of the higher plants. For the general student the most impor- 

 tant thing to realize is that bacteria are unicellular organisms 

 with a cell structure essentially like that of yeasts and other 

 simple plants. This being the case, we shall expect to find that 

 the life processes and activities of bacteria are quite similar to the 

 physiological processes of other fungi. 



Many bacteria have the power of movement in the liquids 

 in which they are developed. These movements, when actually 

 progressive, are due to minute, hairlike protrusions of the pro- 

 toplasm, termed cilia or flagella, which propel the organisms 



OGDGD 



FIG. 135. Diagram showing method of division in bacterial cells 



a, division of a rod bacterium (Bacterium or Bacillus) ; 6, division of a cell 



of a coccus or of a micrococcus form of bacteria. After Novy. Redrawn 



from Marshall's " Microbiology " 



by simple or complex whiplashlike movements. The cilia are 

 variously distributed, being usually either terminal or uniformly 

 distributed over the cell surface. The vibratory movements of 

 bacteria often observed under the microscope are not due to vital 

 activity of cilia or flagella, but resemble the so-called Brownian 

 movements characteristic of fine inorganic particles of various 

 kinds in liquids. 



Reproduction. The bacteria reproduce either by simple division 

 and separation of the two daughter cells or by spore formation. 

 The former process is very rapid and is the usual method of 

 reproduction ; this accounts for the ability of bacteria to multiply 

 with such startling rapidity as is often witnessed in the case of 

 diseases and in decaying or putrefying organic material. 



When a bacterial cell is about to divide (Fig. 135), the cyto- 

 plasm constricts in the middle of the cell from the cell wall 



