270 ; BOTANICAL GAZETTE [ocroBER 
showed a slight growth of the petals, but never opened. Later they 
shriveled and turned yellow. 
Our experiments in which individual 
buds were enclosed and exposed to illu- 
minating gas began with liter flasks in 
which as much as 25°° of gas was used. 
The time of exposure was usually three 
days, starting when the petals were just 
. | | beginning to show. A gradual reduction 
2 Fic. 2.—a, result of treat- of the concentration by reducing the 
Soeas rake ae Thies days amount of gas used and by increasing 
with r part of illuminating gas the size of the enclosure finally located 
mentor a Heaitet he the toxic limit. ‘The highest concent 
same length of time, with part tion did no apparent injury to the vege- 
of ethylene in 500,000. tation; but the effect upon the buds was 
made apparent by a failure to open, by a discoloration and withering of 
the petals, and by the projection of the stigmas. When using 1% of 
illuminating gas to 20,000°, the stigmas still project as shown m 
§- 2, a; 0.5°° of illuminating gas did not suffi- 
ciently retard the growth of the petals to cause 
projection of the stigmas, yet the buds never 
opened farther than shown in fig. 3, although the 
petals remained fresh for several days. Very 
young buds were also exposed to the last con- 
centration of the gas (1 part in 40,000, or 0.0025 
per cent.) for a period of three days. The injury 
Was not apparent at first, and the buds remained 
Sreen for several days, but finally turned brown 
and withered. 
A series of exposures was also made on the 
open flowers. We selected for this work those 
that had just opened, in order to be sure that any ed 
change produced was due to the toxicity of the Fr. 3—Result of 
gas rather than to the natural death of the flower. treating a bud, just 
Here as well as in all the other experiments checks — a three 
were kept. F ig. 4, @ shows a flower before being gave with 1 pes 
corked ina 20-liter carboy; b, the same after being _ ethylene in 4.00% 
