272 BOTANICAL GAZETTE [OCTOBER 
ETHYLENE 
The experiments with ethylene were begun by exposing buds just 
beginning to show the petals to 1, 4, 4, 4, and 4°¢ of ethylene in 
20 liters. 
In each of these concentrations the buds were killed on three days’ 
exposure. The usual signs of gas poisoning were noted; petals 
turned yellow and withered, and the stigmas projected. Since it was 
evident that these concentrations were far above the toxic limit, we 
resorted to the use of a 2 per cent. mixture of ethylene with air. 
Various amounts of this were used, until the toxic limits were definitely 
located. With 2°° of this 2 per cent. mixture in 20,000 (1 part in 
500,000), the results were similar to that obtaining with 1°° of gas 
per 20,000 (1 part in 20,000). In fig. 2, b is a bud just showing the 
petals exposed to this concentration of ethylene for three days. Also 
1°¢ of 2 per cent. ethylene per 20,000 (1 part in 1,000,000) gives results 
similar to that shown by 0.5°¢ of illuminating gas per 20,000 (1 part 
in 40,000). Fig. 3 shows the results of such an exposure for three 
days on a bud just showing the petals. The growth of the petals is 
not sufficiently retarded to make the stigmas conspicuous; the 
petals remain fresh for several days but never open farther. Where 
much less than 1°¢ of 2 per cent. ethylene per 20,000 was used with 
similar buds, three days’ exposure did not prevent their opening. 
When open flowers were exposed to the ethylene, it was found 
that 0.5°¢ of the 2 per cent. mixture in 20,000 (ie., 1 part in 2,000r 
000) caused the closing within twelve hours. The result of such an 
experiment is shown in fig. 4, e. 
It is seen from the data given above that ethylene must form 
approximately 4 per cent. of illuminating gas to be the constituent 
that determines the toxicity of the latter. It becomes necessaTy oe 
to get an estimate of the fraction of the illuminating gas used ne 
is ethylene. We have already stated that no absorbent used in ga 
analysis absorbs ethylene alone. In a special absorption ch gsi 
packed in ice, 50 or more grams of bromin with 150°° of water we 
placed, and measured quantities of illuminating gas passed spat 
When the bromin water was partially discolored, showing 2? alm of 
complete exhaustion of the bromin, the resulting oil (a mixture “ 
ethylene dibromid and other compounds resulting from the erie 
