Section IV., 1913. [43] Trans. R.S.C. 



A Morphological and Cultural Study of some Azotobacter. 



Dan H. Jones, B.S.A., Ontario Agricultural College, Guelph. 

 Presented by Dr. F. C. Harrison, F.R.S.C. 

 (Read May 28, 1913) 



In November, 1910, various samples of soil were obtained from 

 the kitchen garden of the Ontario Agricultural College for the purpose 

 of studying their azotobacter content. The samples were as follows: 



1. Rich surface loam in a high state of cultivation. 



2. Subsoil 18 inches deep — sandy gravel. 



3. Subsoil 30 inches deep — sandy gravel, hard packed. 



4. Old compost well rotted. 



5. New compost not rotted. 



6. Road sand rain washings from College drive. 



Dilutions of each soil were made in sterile water blanks, and from 

 these dilutions inoculations were made into Erlenmeyer flasks of 

 Ashby's solution and plates poured with Ashby's agar. All cultures 

 were incubated at 25°C. (Ashby's solution is composed of mannite 20 

 gms, K2HPO, 0.2 gms, MgSO^ 0.2 gms, NaCl 0.2 gms, CaSO^ 0.1 gm, 

 CaCOg 5 gms, distilled water 1000 c.c. For Ashby's agar, 1^ per cent, 

 agar was added to the solution.) 



Flask Cultures. 



After six days, growth was present in the flask cultures made from 

 surface loam, subsoil 18 inches, subsoil 30 inches, and road sand, but 

 not in those made from compost, either old or new. The growth in 

 each case where it occurred appeared as a whitish, granular, flaky 

 pellicle, easily broken and falling in zoogloea masses to bottom when 

 disturbed. The medium was characterized by cloudiness and there 

 was a flaky, granular precipitate and some gas production was in evi- 

 dence. The growth in the thirty-inch depth sample was much slighter 

 than in the other samples. 



Microscopic observation of hanging drop preparations showed: 



1. Azotobacter as large, coarsely-granular, irregular spheres and 

 short thick rods with rounded ends in ones, twos, threes, fours and 

 dense masses, some forms motile. 



2. Various rod-shaped bacteria, many motile. 



3. Some amoeba and other protozoa. 



4. Some fungus mycelium. 



Sec. IV, 1913—3 



