[Vol. 10 

 28 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



RAW POTATO DISKS 



Sterile disk-shaped slabs from raw potatoes were successfully pre- 

 pared in the same manner as the preceding lot. They were placed 

 in sterile Petri dishes on a piece of sterile wet filter-paper. On the 

 whole, these disks proved to be more usable than the raw potato plugs. 



COHN'8 SOLUTION 



Dissolve 5.0 gnu. KH 2 P0 4 , 5.0 gms. MgS0 4 , 10.0 gms. (NH 4 ) 2 - 

 C 4 H 4 6 , and .5 gm. (Ca 3 (P0 4 ) 2 ) in 1000 cc. distilled water, and filter 

 through paper. Sterilize in autoclave at 15 pounds for 15 minutes. 



uschinsky's solution (modified) 

 The modified solution was made up according to the formula given 



by Smith ('05). 



UHRLICH'S INDOL TEST SOLUTION 



Solution I. — Para-dimethyl-amido-benzaldehyde, 4.0 gms.; 95 per 

 cent alcohol, 380 cc. ; 1IC1 (cone), 80.0 cc. 



Solution 77. — Saturated aqueous solution of potassium persulphate. 



To about 10 cc. of the liquid culture (preferably in Dunham's so- 

 lution and 10 days old), add 5 cc. of Solution I, then 5 cc. of Solution 



II, using separate clean pipettes. Shake the mixture. The reaction 

 may be accelerated by heating to about 70 °C. The appearance of a 

 red coloration which increases in intensity indicates the presence 

 of indol. 



NITRATE BROTH 



Filter, tube, and sterilize in the autoclave 1 gm. peptone ("Bacto"), 

 0.2 gm. potassium nitrate cp. (Merck), and 1000 cc. distilled water. 



REAGENTS AND TEST FOR NITRITES 



Test for nitrites in nitrate broth culture on fifth day by adding: 

 (1) one cc. of a 1 per cent potato starch water; (2) one cc. of a 

 freshly prepared KI water (i.e., KI, 0.2 gm. in 50 cc. distilled water) ; 

 (3) a few drops of strong H 2 S0 4 , (i.e., cone. H 2 S0 4 , 1 part, distilled 

 ILO, 2 parts). The appearance of a blue-black coloration in 10 to 15 

 minutes was taken as positive evidence of the presence of nitrites. 



DETAIL OF COMPARATIVE STUDIES 



MORPHOLOGY 



A detailed study of the morphological characteristics of the 

 several strains at hand was not attempted by the writer. How- 

 ever, it was determined that each was a small, short, actively mo- 

 tile, rod-shaped organism, easily stained by the ordinary aniline 

 dyes. Pairs of the organism occurred in preparations made from 

 fresh cultures on agar slants. No spores were found in any of 

 the cultures, and all were determined to be Gram negative. 



