THE SOIL 



69 



Fig. 2i. — Soil Bacteria Magnified Over 1000 Diameters. 



•1. Micrococcus ureae, produces ammonia from urea; 2. Bacillus flores- 

 cens, produces ammonia in soil; 3. Bacillus subtilis, produces ammonia 

 in soil; 4. Nitrosomonas (after Winogradsky), changes ammonia to 

 nitrite; 5. Nitrobacter (after Winogradsky), changes nitrite to nitrate; 

 6. Clostridium pastorianum, showing spores, free-living nitrogen-fixing 

 organism; 7. Azotobacter chroococcum, free-living nitrogen-gathering 

 bacteria; S. Nodule bacteria from vetch, showing characteristic branched 

 forms ; 9. Nodule bacteria, from soy-bean, showing flagella. 



