198 BOTANICAL GAZETTE [SEPTEMBER 
tight; and enough ethylenet admitted to make the concentration 
about 0.0001 per cent by volume. Both control and treated por- 
tions were then allowed to continue 
development for 72 hours under 
the same conditions (that is, of 
moisture, temperature, and dark- 
ness), except for the ethylene in 
one. At the end of this period 
the epicotyls were collected for 
experimentation. The total cul- 
ture period was g days. 
The epicotyls of the control 
seedlings, at the time of collection, 
were 8-11 cm. in length and verti- 
cal and straight. But the ethy- 
lene treated seedlings showed the 
well known “horizontal nutation” 
Fic. 1.—Etiolated seedlings of the (NELJUBOW 25) or ‘triple re- 
sweet pea, showing the stage of sponse” (KNIGHT and CROCKER); 
development at which the epicotyls that is, the epicotyls were only 
were taken for experimentation: A 
normal; B, ethylene — showing ere long, swollen, and had 
the “triple response”; 3. assumed horizontal or nearly hori- 
zontal positions. The difference 
in appearance between the ethylene treated and the untreated 
seedlings is shown in fig. 1. Certain histological differences are 
shown by the drawings of fig. 2. 
Methods and experimentation 
The present attack of the problem on the effects of ethylene has 
been made through a study of the following questions: (1) chemical 
composition, (2) acidity, (3) osmotic pressure and permeability, 
and (4) respiration. A decided emphasis has been laid upon the 
chemical phase of the problem. 
* The ethylene used in these experiments was ety by dropping ethyl al Icohol 
into syrupy phosphoric acid at a temperature of about 215° C. The final dilutions 
of ethylene were made from a stock ethylene-air mixture containing 2.5 per cent 
ethylene 
