PLATE i 
Large non-sporulating cells. 
Fig. i.—Large cells made up of nuclear material and slime. Azotobacter chroococcum 
(No. 24), Mannite soil extract, 2 days. 
Fig. 2.—Large globular, oval, and rod-like cells, cells of medium size with nuclei. 
A. chroococcum (No. 14). Mannite-nitrate solution, 5 days. 
Fig. 3.—Nuclei of cells of medium size liberated making small cells. A. agile 
(No. 16). Mannite-nitrate agar, 6 weeks. 
Fig. 4.—Liberated nuclear material making regenerative bodies. A. chroococcum 
(No. 22). Mannite-nitrate solution, 7 days. 
Fig. 5.—Large cells producing gonidia and regenerative bodies. A. chroococcum 
(No. 12). Beef agar, 3 weeks. 
Fig. 6.—Regenerative bodies produced by large cells. A. chroococcum (No. 18). 
Beef agar, 5 days. 
Fig. 7.—Large round and rod-like cells. A. agile (No. 16c). Beef agar, 2 days. 
Fig. 8.—Typical mixture of large and medium-sized cells. A . chroococcum (No. 11). 
Mannite-nitrate agar, 1 week. 
Fig. 9.—Typical mixture of medium-sized and small cells in old culture. A . agile 
(No. 16). Mannite-nitrate agar, n months. 
Fig. 10.—Upgrowth from small to large cells. A. sp. (No. 26). Mannite-nitrate 
solution, 5 days. 
Fig. 11.—Liberation of gonidia from regular and irregular cells. A. chroococcum 
(No. 22). Mannite-nitrate solution, 5 weeks. 
Fig. 12.—Spirochaetoid forms, branched and budding cells. A. Beijerinckii (No. 
13). Beef agar, i }4 month. 
