Dec. 17,1917 
Bacterial-Blight of Barley 
633 
incubated for two hours in bouillon. The organism was subsequently 
obtained from this by platings and its pathogenicity proved by inocu¬ 
lations (PI. B, 4; 49, B). 
Further details regarding inoculation experiments are given in a later 
chapter. 
MORPHOLOGY 
Both in the host plant and in culture media the organism is a short, 
actively motile rod, usually single or in pairs except in nutrient pepto¬ 
nized beef broth containing 2 per cent of sodium chlorid, in which it 
forms long nonmotile chains. Growing on peptone beef agar (3-day- 
old cultures), the organism measures 0.5 to 0.8 by 1 to 2.5 m when stained 
with gentian-violet or Ziehl’s carbol-fuchsin. It stains less readily with 
Uoefller’s methylene-blue. 
No spores have been definitely seen. Capsules are formed on agar 
and in milk. The organism is motile by 
means of a single polar flagellum. Re¬ 
peated stainings for flagella both by 
V. A. Moore’s modification of Loeffler’s 
method and by Zettnow’s method agree 
in showing the monotrichous character 
of the organism (fig. 2). It is Gram¬ 
negative and not acid-fast. 
cultural characters 
Unless otherwise specified, these 
have been studied at approximately 
25 0 C., a temperature favorable for the organism. Reference to reaction 
of media is made in terms of Fuller’s scale. Unless otherwise noted all 
reactions were determined by titration with phenolphthalein as indi¬ 
cator, following boiling of solution tested. Notations of color have been 
made in comparison with Ridgway’s Color Standards. 1 
Agar poured plates. —On peptone-beef agar, reaction + 10, colonies appear in 
48 to 60 hours and at end of four days are 1 to 5 mm. in diameter, circular, smooth, 
shining, and amorphous except for inconspicuous somewhat irregular concentric 
striations within the colonies. 2 Margin entire. Colonies are wax-yellow tinged with 
old-gold in color, soft but not viscid in consistency. Buried colonies are lenticular 
or granular (PI, 48, C). 
Agar stabs. —Stabs in +10 peptone-beef agar when 3 days old show a raised, 
smooth, shining, wax-yellow, opaque surface growth 5 mm. in diameter. Growth is 
only at the surface. 
1 Ridway, Robert, color standards and color nomenclature. 43 p., 53 eol. pi. Bibliography, 
p. 42-43. 1912. 
2 These striations within the colonies are evident only under slight magnification, about Xio. and under 
favorable lighting; semidireet lighting best. These striations are so inconspicuous as to have been over¬ 
looked by the writers until Dr. Erwin F. Smith, of the Bureau of Plant Industry, called attention to similar 
colony structure in a closely related organism. 
Fig. a.—-Bacterium translucens: from 96-hour 
growth on potato agar, stained by Zettnow’s 
method to show flagella. X 2,000. 
