2 7 2 BOTANICAL GAZETTE [October 



ETHYLENE 



The experiments with ethylene were begun by exposing buds just 

 beginning to show the petals to i, £, h h and ^ cc 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 CC of this 2 per cent, mixture in 20,000 (1 part in 

 500,000), the results were similar to that obtaining with i cc 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 

 i cc 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 i cc 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 (i e., 1 part in 2,000,- 

 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 necessary now 

 to get an estimate of the fraction of the illuminating gas used that 

 is ethylene. We have already stated that no absorbent used in gas 

 analysis absorbs ethylene alone. In a special absorption chamber, 

 packed in ice, 50 or more grams of bromin with i5o cc of water were 

 placed, and measured quantities of illuminating gas passed through. 

 When the bromin water was partially discolored, showing an almost 

 complete exhaustion of the bromin, the resulting oil (a mixture of 

 ethylene dibromid and other compounds resulting from the reaction 



