The Bacterial Diseases of the Bean 



35 



complete to slight; in curd formation, from none to a solid; and in the 

 amount of peptonization. 



Brom cresol purple milk. A slight yellow-green color appears in about 

 six days, and later a yellow ring is formed. At the end of four weeks, a 

 very soft curd may appear and slight peptonization begins. At the end 

 of eight weeks, the cultures are a greenish brown in color. 



Uschinsky's solution. No growth was observed. 



Fermi's solution. No growth was observed. 



Colin' s solution. No growth was observed. 



Potato cylinders. As a rule, growth appears in twenty-four hours along 

 the streak. It is a light to fair growth, and is pale yellow at first, 

 deepening in seven days to a mustard yellow. The medium may or 

 may not be darkened. Certain strains will scarcely grow on potato. 

 One strain produced a vigorous growth covering the entire cylinder in 

 five days, and was a deep aniline yellow in color. The medium remained 

 unchanged. 



Cellulose digestion. A very light, cloudy growth appears in the liquid, but 

 there is no sign of cellulose digestion. 



Starch agar plates (pH 6.6). Macroscopically there is no indication of 

 starch digestion. Miss Hedges, however, reports that when the cultures 

 are examined microscopically, a slight digestion may be observed. In 

 making determinations, plates were streaked five or six times, and tests 

 for digestion of starch were made at the end of two, six, and ten days. 

 The tests were made by flooding the plates with a saturated solution of 

 iodine in 50-per-cent alcohol. 



Dextrose broth. A cloudy growth appears in the open arm of a fermentation 

 tube within twenty-four hours. A color reaction due to acidity appears 

 in two to three days. The intensity of the reaction varies with the 

 strain, and in all cases the color appears to deepen with age. The 

 following table shows the variation in hydrogen-ion concentration in 

 dextrose broth due to ten different strains. The strains are listed in the 

 order in which thev were isolated. 



