RELATION TO ENVIRONMENT— CLASSIFICATION 39 



As a matter of fact, while the botanical classification of the bacteria 

 offers almost insurmountable difficulties, actual identification is not so 

 complicated a task as this would indicate.. Identification, once roughly 

 made on a morphological basis, is further carried on by the aid of cul- 

 tural characteristics, such as the conditions favorable and unfavor- 

 able for growth, appearance of growth on different media, and pigment 

 formation, by biochemical reactions and by pathogenic properties. 

 The bacteria occupy so important a place in agriculture, in medicine, 

 and in hygiene, that it rarely becomes necessary for a worker in any par- 

 icular field to survey the entire group. The habitat of a large number of 

 pecies is so well known that this consideration alone often givcs a clew 

 Qvaluable for actual identification. 



