46 THE ROYAL SOCIETY OF CANADA 



A, and Aj bear somewhat of a resemblance to Azotobader chroococcum 

 and A, and A, bear somewhat of a resemblance to Azotobader agilis, 

 as described by Beyerinck in the Centralblatt fur Bakteriologie, II 

 Abte., Vol. 7, 1901. 



Description of Varieties. 



Cultural Charaderistics: Growth on Ashby's Agar, — 



Aj. Young surface colonies (1-2 days) at 25°C., having been 

 plated from active growing cultures not more than seven days old, are 

 transparent, colorless, moist, slightly convex, entire, round and about 

 1 m.m. di. 



When one week old, colonies that are not thickly seeded may be 

 from 1-2 cm. diameter, raised, convex, smooth, white, semi-opaque, 

 moist-viscid, glistening, the masses having a tendency to flow, giving 

 irregularity in outline with an entire edge. See PI. I, Figs. 1 and 3. 



Increase in size usually ceases after two to three weeks and a brown 

 pigment is slowly developed like streaky clouds within the viscid mass. 

 As the culture dries with age, the surface becomes irregularly contoured 

 with broad depressions. 



Streak cultures on Ashby agar plates have a similar development 

 to that of the colonies except that after two to three weeks the mass 

 of growth is so great and moist that it frequently flows over the entire 

 surface of the medium. If the streak is on a slanting surface, the 

 growth will flow to the bottom, where it will slowly accumulate until 

 growth on the slope ceases. 



Aj. Surface colonies and streak cultures on Ashby's agar are at 

 first very similar to those of A^. Later, however, they difïer in that 

 they have only a slight tendency to flow over the surface of the medium, 

 being firmer or more pasty, the growth accumulating in a raised mass, 

 with the surface coarsely contoured, more or less concentrically. The 

 mass is first milky white, after two or three weeks it becomes Vandyke 

 brown and later frequently black. See PI. I, Figs. 2 and 4. 



A3. Surface colonies and streak cultures difïer from Aj and Aj 

 in being drier and pasty rather than moist and not having any tendency 

 to flow but developing with upright edges into a raised mass deeply 

 and closely contoured on surface in a rugose manner, often radiating 

 from centre. Cultures at first white, soon turning brown then black. 

 The maximum size of the colonies is considerably less than the maximum 

 size of colonies of Aj and A2. See PI. I, Figs. 5 and 7. 



A4. Surface colonies and streak cultures have a somewhat similar 

 development to those of A,, but difïer in being smaller, more discreet, 

 drier, frequently being cretaceous in texture, the surface becoming 



