18 AGRICULTURAL BACTERIOLOGY 



spores will withstand the temperature of boiling water for 

 sixteen hours. They have been found alive on dried her- 

 barium specimens after ninety-two years, and in the au- 

 thor's laboratory the spores of Bact. anthracis remained 

 alive in water for seventeen years. They are also resistant 

 to chemicals. They assume an important function in the 

 preservation of food and in the prevention of diseases,, since 

 their destruction is often a matter of great difficulty. 



The spore, placed in a favorable environment, germinates 

 and produces a cell similar to the one that formed the 

 spore. Since a cell produces but a single spore, spore 

 formation is. not a matter of growth, but of reproduction. 

 The germination may result in the rupture of the spore at 

 the end, and the young cell emerges with its long axis par- 

 allel to that of the spore. In other types the cell may 

 emerge at the side of the spore. In some instances the spore 

 swells and the spore wall is absorbed in the cell substance. 

 The type of spore germination may enable the differentia- 

 tion of closely related morphological forms to be made. 



Cell aggregates. The arrangement of the cells fre- 

 quently makes possible the recognition of species among 



Fig. 9. Arrangement of Cocci 

 Streptococci, Sarcinae, Staphylococci 



the higher plants and animals. Something of similar na- 

 ture can be used in the study of bacteria. After cell divi- 

 sion has occurred, the daughter cells may separate at once, 

 or the cells may cohere for a time. If the cohering cells 



