1913] KNIGHT & CROCKER—TOXICITY OF SMOKE 369 
if so, it is not in o.o00o1 sufficient concentration to produce the 
response. The other three gases mentioned are not present in the 
smoke in sufficient quantities to be detected by ordinary gas analysis 
methods. Considering the magnitude of toxicity of acetylene and 
propylene, it is impossible that they play any part in the toxicity 
- of paper smoke. The great toxicity of ethylene makes it probable 
that it determines the toxic limit. One part of ethylene in 10,000,- 
ooo of atmosphere inhibits elongation of the epicotyl, 4 parts in 
10,000,000 produce the triple response. The toxicity of paper 
smoke is greatly reduced by washing with bromine, which is further 
evidence that ethylene or some other heavy hydrocarbon is the 
effective gas. 
5. In addition to these gases, tobacco smoke bears hydrogen 
sulphide, ammonia, nicotine, hydrocyanic acid, and pyridine. 
None of these produces the type of response in the seedling caused 
by the smoke, and they exist in the smoke in concentrations far 
below that necessary to determine the toxic limit. The facts stated 
in this paper, along with the work of Motitscu and others, show the 
hazard of using tobacco smoke as an insecticide for greenhouses. 
6. The etiolated epicotyl of the sweet pea is a very delicate test 
for the heavy hydrocarbons (ethylene), exceeding many fold the 
delicacy of any chemical test. 
University oF CHICAGO 
LITERATURE CITED 
“3. ALtEn, I: C., and Burret, G. A., Liquefied products from natural gas; 
their properties and uses. U.S. Bur. of Mines (technical paper) 1031-28, 
Igi2 
. Wivewianns: Hivary, Coke in Encyclopaedia Britannica (11th ed.) 6:655- 
657. 1910. 
3- CouHEN, J. B., and Ruston, A. G., Smoke, a study of town air. pp. 1-88. 
Edward Arnold, London. 1912 
, The nature and extent of air pollution by smoke. Nature 81: 463- 
4. 
5- pag: M. T., and TAauBENHAUS, J. J., The relation of parasitic fungi to 
the contents a the cells of the host plant. I. The toxicity of tannin. 
Delaware Exp. Sta. Bull. 91:1-77. 19tt. 
6. Crocker, Wa., and Knicut, L. I., Effect of illuminating gas and ethylene 
upon ee carnations. Bor. "Gaz. 46: 259-276. I 
