340 BOTANICAL GAZETTE [MAY 
after which it was clamped. This suction served as the force for 
drawing in the gas through the second tube. 
In cases where very large quantities of the gas were required, 
as with methane, the can was replaced by a bell jar and a water 
~ sealused. The whole apparatus was then placed in a dark chamber. 
To make sure of the reliability of the can, this method was also 
frequently used as a check in case of gases demanding only low 
concentration and not readily absorbed by water. If the vapor of 
a very volatile liquid, like ethyl ether, was to be used, a measured 
quantity of it was forced from a pipette into the upturned end of 
one of the glass tubes at a. A glass dish bearing absorbent cotton 
was attached just under the inner down-turned end of the glass 
tube. The liquid volatilized from the cotton and its vapor was 
distributed throughout the can. Applying the gases and vapors in 
this way, at the most distant point from the seedlings, insured 
that they would not at any time receive higher than the finally 
distributed concentration. In case the vapor of a slightly volatile 
liquid, like propyl alcohol, was to be applied, the desired amount 
was dropped on absorbent cotton and quickly sealed in the can 
with the cultures. In this case, of course, the clamps at @ are 
screwed down or the hole provided with a solid cork. 
The cultures are always subjected to the influence of the gas 
for three days, the same period used in our experiments with the 
carnation. At the close of an experiment the epicotyls in any 
culture of controls vary in height from 5 to 13 cm., while the 
cultures subjected to injurious concentrations of gases show less 
growth. 
In this method of experimentation, as is seen, the epicotyls are 
not subjected to the same concentration during the entire three 
days, for the gas is applied only at the beginning of the experiment. 
The concentration must fall to a degree varying with the different 
gases, due to absorption by the plant and substratum, and to some 
extent due to a slow diffusion outward through the seal. If the 
gas is one that is readily absorbed by the plant, as SO., the method 
probably more nearly determines the lethal dose. In the case of 
the carbon-bearing gases (acetylene, ethylene, propylene, methane, 
and carbon monoxide), with the exception of acetylene, which is 
