i6 
C. A. LUDWIG 
removal from the gas, although it took periods of 6 and 5 days respec- 
tively for it to become discernible. 
Bacterium tumefaciens. — There was visible development of B. 
tumefaciens in all percentages of gas except pure gas, although a 
distinct checking effect was observed in the lowest concentration 
used, 25 percent. No development took place in pure gas, but it 
occurred after returning the tubes to the air. The colonies in this 
case became visible in 5-8 days after the removal from the gas. 
BacilMs solanisaprus. — There was a distinct and considerable 
checking of the development of B. solanisaprus in all of the concen- 
trations of gas used, and in the greater ones the development was only 
slight. In the pure gas there was no visible growth, although it did 
occur following the return of the cultures to the air, in which case it 
became visible in 1-5 days. 
Pseudomonas radicicola. — Ps. radicicola proved to be one of the 
more susceptible species. Development occurred in 25 percent gas, 
but it was only slight. At 50 percent concentration and above de- 
velopment was absent, although it occurred following the return to the 
air. The periods of time in which the colonies became visible in the 
cultures removed from pure gas to the air were 12 days and 5 days 
respectively. 
Bacillus mycoides. — There was at least a very slight development 
of B. mycoides in all of the concentrations of gas used, but the 25 per- 
cent strength showed a slight retarding action, since it took 3 days for 
the colony to cover the slant from a spot inoculated in the center while 
in the air the slant was covered in 2 days. The development remained 
very slight in the higher percentages throughout the 6-day duration 
of the tests. The very slight colony developed in the case of the 50 
percent and 85 percent gas, where the inoculation was by streak, was 
very similar in appearance to that of B. subtilis in concentrated gas. 
After being removed to the air normal development began in from 2 
to 5 days and soon covered the slants. It did not originate all along 
the streaks, however, but at isolated points, so that separate colonies 
were formed, as if a partial sterilization of the slant had been produced 
by killing the inoculating bacteria between the points where the 
colonies arose. 
A number of fungi were grown in Petri plates and the effects of 
illuminating gas noted, chiefly by measuring the diameter of the 
colonies at 3-day intervals (in some instances the sum of two different 
