380 BOTANICAL GAZETTE [ DECEMBER 
Usually the organism is motile, but the motion is always 
slow. Motility is to be seen in colored as well as in colorless 
individuals. It stains well by the ordinary methods and retains 
the stains by the method of Gram and that of Claudius. Greater 
morphological details would take us beyond the scope of the 
present note, namely, an account of some of the results of the 
study of the pigment produced by this bacillus on potatoes and 
on gelatin. 
Growth on potatoes and the pigment formed.—On a medium as 
variable in composition as potatoes of different varieties and 
different ages of growth, it might be expected that there would 
be considerable variation in the colors of the pigment and nature 
of the growth of a chromogenic organism. The B. polychromo- 
genes shows the effect of such changes in a most marked manner. 
Potatoes upon which this organism grows are colored variously 
yellow, greenish, red, violet, blue; the last color predominating 
but not constant. It was soon found, however, that a beautiful 
deep blue could be obtained, almost without fail, if the potatoes 
were first soaked in a dilute solution of sodium hydroxid (0.25 
per cent. to 0.50 per cent.) containing a little calcium phosphate 
for twenty-four hours or less, depending upon the thickness of 
the pieces. Since this medium has served as the basis for the 
isolation of the pigment, and is being constantly employed by 
us in the study of the pigments of other chromogenes, it may 
not be out of place to describe our methods of preparation. 
As large tubers as possible are chosen, such as are known to 
become mealy and porous on boiling. They are well washed in 
cold water, using a brush to aid in cleansing, and are dropped 
into boiling water with the skins on, and boiled till just cooked 
through. The water is then poured off, the potatoes allowed to 
cool somewhat, pealed, cut into slices 1 to 2™ thick, and dropped 
into a dilute solution of sodium hydroxid, where they remain 
about eighteen hours. The supernatant liquid is then poured 
off, the slices drained and transferred to glass boxes tole aa o 
diameter and 49 to 50™ deep, with loosely fitting covers (in 
other words deep Petri dishes), a little water is added, and the 
