14 



AGRICULTURAL BACTERIOLOGY 



vature may be very slight, or it may be a true spiral. The 



rigidity of the bacterial 

 cell is well illustrated in 

 the spiral forms. It is 

 evident that there may 

 be a gradual gradation 

 in form from the round- 

 ed coccus type through 

 to the spirilla. 



Frequently under the 

 conditions of growth in 

 the laboratory and less 

 frequently in nature, 



Fig. 2. Cocci 

 A spherical organism in which the cells 



occur in irregular shaped masses is called 

 a staphylococcus After Giinther. 



cells of abnormal shapes 

 are noted, known as in- 

 volution forms. It is 

 commonly believed that these cells are degenerate forms 

 and are not capable of 

 reproduction. The de- 

 viation from normal cell 

 type is probably occa- 

 sioned by growth under 

 unfavorable conditions. 



Reproduction. - - The 

 bacterial cell divides 

 into two daughter cells 

 by an infolding of the 

 protoplasm in the mid- 

 dle of the cell until the 

 protoplasm is completely 

 divided. The cell wall 

 is then formed, and fin- 



Fig. 3. Large Bacilli 



L rod-shaped organism in which the cells 

 occur in chains is called a streptobacillus 

 After Giinther. 



ally splits, forming the 

 opposing ends of the new cells. 



In the case of bacilli and 



