270 



BOTANICAL GAZETTE 



[OCTOBER 



Fig. 2. — a, result of treat- 

 ing a bud, just beginning to 

 show the petals, for three days 

 with 1 part of illuminating gas 

 in 20,000; b, result of the treat- 

 ment of a similar bud, for the 

 same length of time, with 1 part 

 of ethylene in 500,000. 



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 cc of gas was used. 

 The time of exposure was usually three 

 days, starting when the petals were just 

 beginning to show. A gradual reduction 

 of the concentration by reducing the 

 amount of gas used and by increasing 

 the size of the enclosure finally located 

 the toxic limit. The highest concentra- 

 tion did no apparent injury to the vege- 

 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 i cc of 

 illuminating gas to 20,000", the stigmas still project as shown in 

 fig. 2, a; o.5 cc 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 

 green 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 

 change produced was due to the toxicity of the 

 gas rather than to the natural death of the flower. treating 3 a _ bud, U just 

 Here as well as in all the other experiments checks beginning to show 

 were kept. Fig. 4, a shows a flower before being *y^' ^^ 

 corked in a 20-liter carboy; b, the same after being ethylene in 1,000,000. 



