1913] KNIGHT & CROCKER—TOXICITY OF SMOKE 361 
Various amounts of nicotine (1-30 drops) were placed on filter 
papers and sealed in 1o-liter cans with cultures. Only the smaller 
amounts completely volatilized, but in 
none was any inhibition of growth notice- 
able. The test seedlings in culture cans 
of various sizes, bearing several grams of 
pulverized KCN, showed no inhibition of 
growth. In this connection it should be 
stated that HCN exists in such small 
quantities in tobacco smoke (o-6o mg. 
from 100 gm. of tobacco) that LEHMANN 
(18) does not take it into consideration 
as a toxic factor with the smoker. It is 
certainly much less to be considered in 
plants to which it is rather slightly toxic. 
a TC . 
4.—Responses to CO: a, check; b, 50 cc. of CO in to liters; c, 100 cc. of CO 
in Io hth d, 200 cc. of CO in ro liters. 
The following table (p. 362) shows the nature of the responses 
caused by other constituents of tobacco and paper smoke and the 
concentrations necessary to produce them. 
In this table inhibition of growth corresponds to the sixth 
response of Netyusow, declination to the fifth, and horizontal 
nutation and swelling to the third. Only 4 of the 30 or more com- 
mon gases and vapors whose effect on this organ we have studied 
certainly produce “declination” or “horizontal nutation and swel- 
ling.”” They are ethylene, acetylene, propylene, and carbon monox- 
ide. This does not include the mixtures of gases (illuminating gas 
