30 
C. A. LUDWIG 
3. Different species exhibit different degrees of tolerance for the 
gases, and in general a species which is relatively intolerant of one is 
relatively intolerant of others. 
4. There was no real evidence that the continued culture of an 
organism in illuminating gas induces the development of an increased 
tolerance for the gas by the strain so cultivated. On the other hand 
there was some slight indication that the vigor of a strain so cultivated 
is slowly low^ered. 
5. The colony habit of organisms is often modified more or less 
strikingly in the more toxic gases. This is exemplified especially in 
the color variations of B. Kieliensis, the decrease in colony mass and 
gross appearance in B. Kieliensis, B. subtilis, and B. mycoides, and 
the more compact, upright arrangement of hyphae in several fungi. 
6. Ethylene and methane are relatively less inhibitory to the 
organisms used than is illuminating gas, but carbon monoxide is 
about equal to the illuminating gas in this respect. 
7. The effect of the gas cannot be laid to any one constituent, 
but is probably the sum of the small effect of each plus the greater 
effect of a deficient oxygen content. 
8. Incidentally the foregoing results indicate that the amount of 
illuminating gas often present in laboratory air is not a menace to 
scientific results in bacteriology and mycology. 
The writer takes pleasure in extending thanks to Professor F. C. 
Newcombe for suggestions and help tendered during the prosecution 
of this study, and also to all others who have helped in forwarding it. 
University of Michigan, 
Ann Arbor, Michigan 
LITERATURE CITED 
1. Crocker, "William, and Knight, Lee I. Effect of Illuminating Gas and Ethylene 
upon Flowering Carnations. Bot. Gaz. 46: 259-276. 1908, 
2. Toxicity of Smoke. Bot. Gaz. 55: 337-371. 1913. 
3. Doubt, Sarah L. The Response of Plants to Illuminating Gas. Bot. Gaz. 63: 
209-224. 1917. 
4. Frankland, Percy. Ueber den Einfluss der Kohlensaure und anderer Gase auf 
die Entwickelungsfahigkeit der Mikroorganismen. Zeitsch. Hyg. 6: 13-22. 
1889. 
5. On the Influence of Carbonic Anhydride and Other Gases on the Develop- 
ment of Micro-organisms. Proc. Roy. Soc. Lond. 45: 292-301. 1889. 
6. Girardin, — . Einfluss des Leuchtgases auf die Promenaden- und Strassen- 
baume. Jahresber. Agrik. 7: 199-200. 1864. (Not seen.) 
