368 BOTANICAL GAZETTE [MAY 
analysis methods are inadequate. To the experimenter in plant 
physiology it furnishes an excellent means of making sure that the 
laboratory air is sufficiently ‘‘pure” not to interfere with plant 
response, while to the practical greenhouse man. it furnishes a 
means of determining the probability of injury from illuminating 
gas or other mixtures bearing ethylene. 
Summary 
1. The smoke from tobacco cigars and cigarettes which has been 
thoroughly washed in 15 per cent H,SO, and 4o per cent NaOH 
is very toxic to the etiolated epicotyl of the sweet pea. In the case 
of cigar smoke thus treated, 1000 parts per million of atmosphere 
give a triple response: reduction of rate of elongation, swelling, 
and diageotropism of the portion growing in the impurity; 5000 
parts per million of atmosphere completely stop elongation and 
produce a swollen knob, while the epicotyl remains vertical; still 
higher concentrations kill the epicotyl before any form change 
occurs. 
2. On the basis of dry weight burned, the washed smoke from 
cellulose paper cigarettes is even more toxic. The characters of 
the responses produced are identical with those produced by smoke 
from tobacco cigars and cigarettes. 
3. When smoke from equal amounts of cellulose paper, smoked 
as a cigarette on one hand, and burned as an open sheet on the other, 
are compared, it is found that the former is 50 times as toxic as the 
latter. Higher oxygen supply during burning greatly reduces the 
toxicity. A large part of the toxic gases are undoubtedly oxidized 
to CO, and H,0. 
4. In the cigarette smoke of cellulose paper the following gases 
are present: carbon dioxide, carbon monoxide, acetylene, ethylene, 
methane, and some higher homologues of the last three. Washing 
out the carbon dioxide does not reduce the toxicity of the smoke, 
nor will carbon dioxide produce the type of response produced by 
the smoke. Carbon monoxide, acetylene, ethylene, propylene, 
and perhaps methane produce the same type of response as smoke. 
Carbon monoxide is in 0.015 sufficient concentration to determine 
the effect of smoke. It is not certain that methane is toxic at all; 
