148 Journal of Agricultural Research vo1.xix,no.4 



CULTURAL CHARACTERS 

 I. — STOCK HALO ORGANISM 



Morphology. — The organism is a motile rod with rounded ends (PI. 

 34, B, E), sometimes occurring singly or paired, but usually in short 

 to long chains (PI. 34, C). Organisms grown on beef-peptone agar and 

 potato agar and stained with Ribbert's capsule stain, gentian violet, and 

 carbol fuchsin measure from i to 4 /x in length and from 0.4 to 0.8 (x in 

 width, with an average of 0.65 by 2.3 ju. Stained by the Van Ermengen 

 method from 24-hour cultures on beef-peptone agar, the organism shows 

 from one to several polar flagella about the same length as the organism 

 or only a little longer (PI. 34, E). No spores have been observed, 

 although special staining methods with hot carbol fuchsin and methylene 

 blue were used. Capsules are formed on both potato and beef-peptone 

 agar and were stained with Ribbert's capsule stain (PI. 34, D). Compact 

 pseudozoogloeae are not formed — that is, there is little or no viscidity. 

 No branched forms have been observed. 



Nutrient broth. — Beef-peptone bouillon ( + 10) shows light clouding 

 in 24 hours at 25"^ C. In 5 days there is moderate uniform clouding, 

 and a flocculent white film or pellicle forms on the surface and falls to the 

 bottom of the tube in small white flakes. On further shaking the flakes 

 disappear. In older cultures there may be no pellicle but merely a slight 

 ring around the surface. The clouding is never very heavy, and the thin 

 surface film soon disappears. The medium is gradually changed in color 

 until at the end of 60 days it is a deep amber brown.* The odor of decay 

 is distinct with more or less of the penetrating smell of ammonia. The 

 sediment in cultures from recent isolations is loosely flocculent. There 

 was a somewhat viscid swirl in some of the old broths containing sodium 

 chlorid. Rectangular crystals form at the surface. 



Broth plus absolute alcohol. — To 10 cc. of 4-15 beef-peptone 

 bouillon absolute alcohol was added to make 4, 5, 6, and 7 per cent. 

 There was heavy clouding in 4 and 5 per cent, moderate clouding in 6 per 

 cent, and slight clouding in two out of three tubes of 7 per cent. 



Agar stroke. — On +10 beef- peptone agar slants growth in 2 days is 

 moderate, flat, undulate, white, shining, translucent, slightly contoured, 

 butyrous. The medium is slightly browned. There is a slight odor of 

 decay. 



On potato-dextrose agar slants the growth in 2 days is abundant, 

 slightly undulate, raised, glistening, smooth, opaque, white, of gelatinous 

 consistency (PI. 30, B, h). The medium is unchanged and there is no odor. 



Agar colonies. — (i) On poured plates of -j-io ^ beef-peptone agar 

 from -f 10 broth cultures, colonies appear after 30 hours at 25° C. as tiny 

 translucent dots. When 2 days old the colonies are i to 2 mm. in diame- 



' RiDGWAY, Robert. coi,or standards and color nombnclature. 43 p., si col. pi. Washington, 

 D.C. 1912. 

 ' Fuller's scale. 



