Mayis, I920 Halo-Blight of Oats 157 



Blood serum . — Growth was moderate, filiform, slightly raised, orange- 

 yellow, smooth, shining. In 2 weeks the center of the growth became 

 red, but the author was unable to verify this change in 191 9. The 

 medium was unchanged. 



Litmus sugar agars. — In 24 hours there is a slight reddening of 

 litmus dextrose agar and in 3 days reduction has begun in the lower end 

 of the tubes, the upper two-thirds being rose red. Litmus-lactose and 

 litmus-maltose agar show reduction in the lower ends of the tubes in 

 3 days. These tubes are red through the center and blue at the top. 

 At the end of a week all agars are colorless at the bottom of the tubes, 

 red in the center, and blue toward the top. Growth is abundant. At 

 the end of 2 weeks the colony begins to turn red. 



Starch agar. — There is no diastasic action on starch. 



Indol.— Indol production is feeble. 



Nitrate bouillon. — No gas is produced in fermentation tubes. 

 Nitrates are not reduced. 



Ammonia. — Ammonia production is moderate. 



Hydrogen sulphid. — No hydrogen sulphid is produced. Tests were 

 made with lead-acetate paper over broth and with lead-carbonate agar. 



Optimum reaction and toleration limits. — By the use of sodium 

 hydroxid and hydrochloric acid, using phenolphthalein as indicator, 

 beef-peptone bouillon was adjusted to each of the following reactions: 

 -f 25, -t-2o, 4-15, +5, o, —5, —6, —13, —15, and -22. These were uni- ^ 

 formly inoculated from broth cultures and kept at 24° C. In 24 hours 

 there was clouding in all except +20 and +25. At the end of 3 days 

 there was clouding in all except -{-25. The clouding in -I- 20 was slight. 

 At the end of i week there was no growth in +25, light clouding in 

 -f 20, — 15, and — 22, and heavy clouding in all the other reactions, with 

 precipitation and surface growth. In 3 weeks there was clearing in 

 — 15 and —22, but a viscid yellow precipitate. There was never any 

 growth in +25. The optimum reaction for growth is -f5 Fuller's scale. 



Gas formation and aerobism. — Tests were made in fermentation 

 tubes in the presence of the following carbon compounds: dextrose, sac- 

 charose, lactose, maltose, mannit, and glycerin. A 2 per cent solution 

 of each was made in a 2 per cent water solution of Difco peptone. Bacil- 

 lus coli Escherich was used as a control and produced gas in each solution. 

 No gas was produced by the yellow organism. There was clouding in 

 the open arm of all tubes in 2 days, the heaviest growth being in saccha- 

 rose and maltose. In 3 days clouding began in the closed arm of tubes 

 containing saccharose and mannit. At the end of a week there was 

 clouding in the closed arm of all tubes— heavy in glycerin and mannit, 

 light in dextrose, and moderate in the others. Tests for ammonia with 

 Nessler's reagent gave a positive reaction in all sugars — slight in glycerin, 

 and moderate in the others. Titrations with phenolphthalein as indica- 

 tor showed no acid production. The hydrogen-ion concentrations were 



