332 DAN H. JONES 



2. Individual cells following a period of reproduction by fission, 

 may develop reproductive granules or gonidia, within their cell 

 plasma, which, on disintegration of the mother cell are dispersed, 

 increase in size, become typical azotobacter short rods, ovals 

 or spheres, and reproduce by fission. The young cells are motile. 



3. The reproductive granules vary in size, some being very 

 minute. Attempts to pass them through a Berkfeld filter were 

 not successful. They are positive to Neisser's blue and to 

 Heidenhain's iron haemotoxylin stains. 



4. Another type of granule, not reproductive and not stainable, 

 possibly composed of reserve food substance, is found associated 

 with the reproductive granules in the mother cell. 



5. A "symplastic stage" as described by Lohnis and Smith, 

 has been observed in cultures varying in age from a few days 

 to several weeks. In this symplastic stage aggregations of cells 

 coalesce, the cell walls appear to break down and the plasma of 

 the various cells intermingles, with the resultant production of 

 regenerative granules varying in size from very minute bodies, 

 scarcely discernible with the oil immersion lens, to larger forms 

 that are readily visible when stained. Neisser's blue is a good 

 stain for showing up these granules. On- emergence from the 

 "symplasm" these granules grow into young azotobacter cells 

 and reproduce by fission. 



6. Varieties 1 and 2 in cultures up to fourteen days old on 

 Ashby's agar produce large capsules; variety 3 produces only 

 small capsules and variety 4 produces no capsules. 



7. All four varieties are motile in young cultures on Ashby's 

 agar or in Ashby's solution. 



8. In cultures more than fourteen days old, large, spherical, 

 thick-walled cells are common. In varieties 1, 2 and 4 these 

 occur in irregular groups; in variety 3 they occur in tetrads and 

 sarcina packets. These appear to be resting cells or arthrospores, 

 as at this stage multiplication by fission appears to have ceased 

 for the time being. On transference to fresh media these thick- 

 walled cells germinate, the cell plasma emerging from the thick 

 wall as a large rod which at once proceeds to multiply by fission; 

 the young cells are motile. 



