New YorRK AGRICULTURAL EXPERIMENT STATION. 53 
cane-sugar may be increased to ten per cent., the magnesium sul- 
fate to one per cent., the monobasic potassium phosphate to two 
per cent., or the amounts may be lowered below the quantities 
first mentioned. In the latter case, however, the food materials 
are more quickly used up. The organism multiplies as long 
‘as the materials in solution are not exhausted. Other compounds 
may be used as sources of magnesium, potassium, and phosphoric 
acid. Although I usually leave nitrogen out of the culture me- 
dium at this stage, its absence is not essential, as the object of the 
first step is simply to separate the organisms into pure cultures 
free from mold or other contamination, the process of separating 
out in this fashion being familiar to all bacteriologists and in 
common use. They grow best between 20° and 30° ‘centigrade, 
and light or its absence is immaterial. When pure cultures are 
thus obtained, the organism is transferred immediately, or after 
several weeks, if desired, by any of the bacteriological transfer 
methods in use to water containing about one per cent. cane- 
Sugar or maltose, (tke latter being the better,) about .02 to .05 
per ct. magnesium sulfate, and about 0.1 per ct. monobasic potas- 
sium phosphate, or equivalent sources of magnesium, potassium, 
and phosphorus, as in the case of the first-described medium. 
The quantities used may here also vary, as stated above; but the 
per cents. given have been found to be the most favorable for 
growth under ordinary conditions. One cubic centimeter of the 
culture will suffice for impregnating one hundred liters of the 
fluid. Any kind of container or vessel that can be easily cleaned 
will serve for this purpose; but Erlenmeyer flasks are best where 
small quantities are to be cultivated under antiseptic conditions. 
In this solution, which should be kept between 20° and 30° centi- 
grade, in light or in darkness, as desired, the organisms in- 
crease very rapidy and have to obtain all of their nitrogen in the 
free state from the atmosphere or from the atmospheric nitrogen 
in solution in the medium. ‘This liquid culture solution, even 
when in large quantity, will in a few days become milky in 
appearance by the presence of immense numbers of the developing 
organisms. The water containing the organisms, where direct 
use is desired, is then sprinkled upon seeds or soil; but for the 
purposes of preservation and distribution the following steps are 
taken: Absorbent cotton or other equivalent material is dipped 
