Jan. is, 1917 
Blackleg Disease of Potato 
123 
Capsules, none. 
Pseudozoogloea, present, slight. Involution forms, not observed. (Reported 
by Harrison for B . solanisaprus, at higher temperatures.) 
Staining reactions. Stains well in aqueous gentian violet, anilin water gentian 
violet, aqueous methylene blue, alkaline methylene blue, aqueous fuchsin, 
carbol fuchsin. Oram, negative. 
II. CULTURAL FEATURES 
Agar stroke. Growth, moderate. Form of growth, filiform. Elevation, flat to 
slightly raised. Luster, glistening. Topography, smooth. Optical characters, 
slightly but distinctly bluish opalescent. Chromogenesis, pearly white. Odor, 
absent. Consistency, butyrous—some strains slightly viscid, others not. 
Potato. Growth, moderate to abundant. Form of growth, filiform to spreading. 
Elevation, first convex, then slightly raised to flat. Luster, glistening. Topog¬ 
raphy, smooth to slightly rugose. Chromogenesis, yellowish white, later dirty 
white.. Slight odor of decayed potatoes in old cultures. Consistency, butyrous— 
some strains slightly viscid, others not. Medium, slightly grayed at first, later 
plainly grayed. 
Agar stab. Growth, slightly best at top, abundant, widespreading. Line of punc¬ 
ture, filiform to slightly papillate. 
Gelatin stab. Growth, best at top. Line of puncture, filiform. Liquefaction, 
infundibuliform to slightly napiform, later may be saccate, occasionally crateri- 
form to stratiform. Begins in 1 to 3 days at 20° C. Complete in 7 to 10 days 
with some cultures, in others not complete in 60 days. 
Nutrient broth. Surface growth, usually slight ring and occasionally slight granular 
pellicle in young cultures. Clouding, moderate to strong, persistent. Medium, 
not discolored. Odor, absent. Sediment, compact, scant, granular, and dirty 
white—some strains slightly viscid, others not. 
Milk. Coagulation, usually not until the seventh day at 20° C. Coagulum, not 
digested or at the most very slowly peptonized. Medium, not discolored. 
Litmus mifk. Acid, litmus reduced. 
Gelatin colonies. Growth rapid at 20° C. Form, round. Edge, entire. Liquefac¬ 
tion, saucer. 
Agar colonies. Growth, rapid at 20° C. Form, round, occasionally irregular, buried 
colonies, lens-shaped to slightly ovoid or spherical. Surface, smooth. Eleva¬ 
tion, flat to slightly raised. Edge, buried colonies, entire, surface colonies, 
entire to undulate. Internal structure, finely granular. Color buried colonies, 
brownish yellow under a 16 mm. objective and 6 ocular, slightly yellowish under 
hand lens, surface colonies, pearly white, bluish opalescent to transmitted light. 
Fermi’s solution. Growth, first moderate, later abundant. 
Cohn’s solution. Growth, absent. 
Uschinsky’s solution. Growth, copious. 
Sodium chloride in bouillon. Growth inhibited, 3 per cent, slightly, 4 per cent;some, 
and 5 per cent, considerably. 
Growth in bouillon over chloroform. Growth, much restrained at first, later moderate. 
Best medium for long-continued growth. Neutral beef bouillon. 
III. PHYSICAL AND BIOCHEMICAL FEATURES 
Fermentation tubes. Gas produced from dextrose, saccharose, lactose, maltose, and 
mannit, but not in glycerin and dextrin. Growth in the closed arm with dex¬ 
trose, saccharose lactose, maltose, mannit, and dextriii, but either absent or 
slight with glycerin. Acid produced from dextrose, saccharose, lactose, mal¬ 
tose, mannit, and glycerin. 
