324 BACTERIA IN RELATION TO PLANT DISEASES. 
reduced the litmus in course of a few days, except at the top. On some vegetable media, 
and with various sugars, a feebly acid reaction was sometimes detected, but the nature 
of the acid is unknown. Possibly sometimes the writer may have had contamination 
in his cultures, since Harding has found in some of his cultures a contaminating organism 
having the group number 211.2223532. The subject is open to further study in which 
connection the interesting pages 31-33 of Harding’s paper (1910) should be consulted. It 
does not grow luxuriantly in Fermi’s solution, Uschinsky’s solution, or Cohn’s solution, 
usually it does not grow at all in the latter and when it does there is no fluorescence. In 
Fermi’s solution after 2 weeks there was thin clouding, no pellicle, and a scanty pale pre- 
cipitate. It will not grow in an atmosphere of hydrogen, nitrogen, or carbon dioxide. In 
vacuo it also grows feebly in proportion to the completeness of the exhaustion of the air. 
It will not grow in peptonized beef-broth to which chloroform has been added. This 
experiment was repeated in February 1906, with the same result (fig. 130). Four tubes > 
inoculated February 12 remained entirely free from clouding (February 24).. It is promptly 
killed in agar plates by direct sunlight (30 minutes or less). Z 
It produces a brown pigment soluble in water, and a yellow pigment insoluble in water 
but soluble in glycerin, ethyl alcohol, methyl alcohol, acetone, ammonium carbonate, or 
glacial acetic acid. This yellow pigment appears to be associated with a fat, 7. ¢., it is a 
lipochrome. Harding states that the yellow pigment is soluble in ethyl and methyl alcohol, 
is unchanged in glycerin, and is darkened in carbon-bisulphide, xylene, gasoline and chloro- 
form. He found it slowly destroyed in dilute acetic acid, and destroyed in sulphuric ether, 
dilute hydrochloric acid, sulphuric acid, and nitric acid. The writer found the yellow 
pigment bleached by contact with carbon-bisulphide, xylol, toluol, ether and chloroform. 
The color is lodged in the organism itself. The brown pigment is not formed in beef-broth, 
or in peptone-water with grape-sugar. 
The minimum temperature for growthis 5° C. or thereabouts. Itsoptimum temperature 
is 30° C. or thereabouts. Its maximum temperature is 38° to 39° C. The thermal death- 
point is 51°-+C.* 
It tolerates sodium hydrate in peptonized beef-bouillon up to —4o, and plant acids up 
to + 30 or +40 (?). 
Young cultures stain readily with various basic anilin dyes. Harding usually obtained 
a polar stain with Ziehl’s carbol-fuchsin. In agar cultures 20 days old he says many of the 
individuals stain feebly with methylene blue unless it is heated or applied for a long time. 
In sections of the tissues the organism stains very satisfactorily with Ziehl’s carbol-fuchsin 
(3 to 5 minutes’ exposure), with nigrosin, and with Heidenhain’s iron haematoxylin. Hecke 
reports better success with Benda’s iron haematoxylin than with carbol-fuchsin, 7. e., clearer 
sections. With this stain, by proper differentiation, it is possible to obtain fine contrasts, 
i. e., the bacteria remain black on a pale background. He used weak acetic acid after 
carbol-fuchsin for differentiating. Good contrasts may be secured also by a suitable contrast 
stain, ¢. g., methyl green (2%) in water 18 hours; solid green, sat. water sol., 1 minute. 
Brenner states that the organism grows readily in Fischer’s nutrient mineral solutiont 
with cane-sugar for the carbon food and nitrate of potash as the only nitrogen food. In 
other words, following Fischer’s classification, it is nitrobacterium. It also grows well, 
according to Brenner, in Fischer’s nutrient mineral solution with addition of grape-sugar 
and asparagin or ammonium tartrate as the nitrogen food. It grew moderately in the same 
*Harding reports great variations in the thermal death-point, depending on age of culture, length of time grown 
on artificial media and temperature at which culture was grown. His highest thermal death-point is 52° C., the lowest 
44° C. For the writer’s method of making thermal death point tests see Vol. I, page 77. 
p. ct. 
Pistilled waters i Aiod teapeeee oho 100.00 
Dipotassium phosphate................. 1.00 
Magnesium sulphate sisc otis sient eases 0.20 
Calcium: chiondes coe cas sors Cease 0.01 
