226 Journal of Agricultural Research voi. xvi, No. s 



DESCRIPTION OF THE ORGANISM 



The caustive organism of angular-leafspot appears to be an unde- 

 scribed species, and a description is therefore appended. 



Bacterium angulatum, n. sp. 



As it occurs in the plant and also on media, the organism is a short rod with rounded 

 ends, single or in pairs, 0.5 m wide by 2 to 2.5 m long. No spores are produced, and no 

 capsules have been demonstrated. It is motile by means of a small tuft of flagella 

 at one pole, demonstrated by the Van Ermengen silver-nitrate method. The number 

 of flagella varies from about three to six, and they are slightly longer than the body 

 of the bacterium. It stains readily with the ordinary dyes, and is Gram-negative 



and not acid-fast. 



TEMPERATURE RELATIONS 



The best growth is obtained at temperatures between 17° and 20° C. 

 There was no growth at 37.5° C. 



CULTURAL CHARACTERS 



Agar plates. — Colonies are visible in 48 hours at 20 to 22° C. They increase slowly 

 in size, being less than i mm. in diameter at three days. After seven days the largest 

 are 4 mm. in diameter and the average about 3 mm. The maximum size attained is 8 

 mm. They are roimd, smooth, convex, shining, opalescent at first, later becoming 

 dull white with a slight creamy cast and develop an opaque center with a clear margin. 

 They are finely granular under the compound microscope, with a slightly undulate 

 margin. Buried colonies are lenticular. 



Agar slants. — Growth is slight in three days, the line of the stroke being about 

 I mm. broad, and is not more than 5 mm. broad after one month. The growth is 

 filiform, slightly raised, shining, smooth, and slimy. Considerable white sediment 

 is formed at the base. The medium attains a slight pale-green fluorescence. 



Gelatin plates. — Colonies are visible in 48 hours as small points similar to those 

 on agar. Liquefaction is rapid, beginning in cuplike hollows in 48 hours. The 

 cupules are 5 to 10 mm. broad in 3 days. Thickly sown plates are completely liquefied 

 in 48 hours. 



Gelati.n stabs. — Liquefaction is infundibuliform and begins in 24 hours. As 

 liquefaction progresses, the upper part becomes stratiform, and the lower maintains 

 the blunt funnel form. Liquefaction is complete within 15 days at 18° to 20° C. 



Beep bouillion. — Uniform heavy clouding occvirs within 48 hours. No surface 

 scum or pellicle is produced, and there are no zoogleae. A grayish precipitate forms 

 in old cultures. 



Beep bouillion with sodium chlorid. — Two per cent sodium chlorid produced 

 only a slight inhibition of growth in 48 hours. Heavy clouding was present at seven 

 days with 2 per cent of sodium chlorid, but gro^vth was practically inhibited with 4 

 per cent of the salt. 



Potato c\'Linders. — The form of growth is similar to the agar slant but with a 

 slight dull yellow pigment. 



Milk. — Inoculated milk clears slowly and without coagulation. The protein is 

 digested. Clearing begins within seven days in definite layers from the top downward, 

 and is complete within three weeks. The liquid is only faintly translucent at this 

 time and is near Ridge way 's pale fluorite green. 



Litmus milk. — Lavender-colored litmus milk becomes blue from the top down- 

 ward in definite layers. The color change begins on the second or third day and is 

 complete within 14 days. During two months the medium remained dark blue and 

 liquid. 



