28 



Bacteria in Relation to Country Life 



present in a considerable number of species, among 

 them the nodule bacteria of the legumes. It is appar- 

 ently stored up by the organisms as a reserve food- 

 material. Another carbohydrate, designated as granu- 

 lose, has been found to occur in a well-defined group of 

 organisms. 



Fats and wax-like substances may also constitute a 

 more or less considerable portion of the bacterial cells. 



Fig. 12. Microscope and accessories for bacteriological work. 



In the germ of tuberculosis, the cells have been found to 

 contain 26.5 per cent of fat and wax in their dry sub- 

 stance. The nitrogen-fixing organisms of the azoto- 

 bacter group frequently store up very considerable 

 quantities of fat in their cells. Some species are observed 

 to do this more than others. 



The so-called sulfur bacteria, found in some sulfur 

 springs and in the sea, deposit within their bodies little 



