764 
Journal of Agricultural Research voi. xxvn, no. io 
lot were still green, those in the second lot (ethylene i to 1,000) were 
yellow, and those in the first lot (ethylene 80 per cent) were slightly 
more yellow than the controls but not more than one-eighth colored, 
the buttons being firm on all but one. High concentrations of ethylene 
appear to retard the rate of coloring. 
LACK OF OXYGEN 
Pure nitrogen, generated from ammonium chlorid and sodium nitrite, 
was collected over water in a 19-liter bottle. To this nitrogen ethylene 
was added to make a concentration of 0.5 per cent by volume. By 
water displacement this gaseous mixture was pushed over into a desic¬ 
cator containing green lemons. In order to remove the oxygen as com¬ 
pletely as possible, the bottom of the desiccator was covered with alkaline 
pyrogallate, which was also placed in wash bottles through which the 
gas was bubbled before entering the desiccator. For comparison, 
another lot of fruit was treated in an exactly similar manner except that 
outdoor air was used instead of nitrogen and water was substituted for 
alkaline pyrogallate. Fresh quantities of gas were pushed over into the 
desiccators each day. The control lot was colored yellow at the end of 
eight days but the lot receiving no oxygen remained green. A duplicate 
experiment, using 1 per cent of ethylene, gave similar results. Oxygen 
appears to be necessary for coloring. 
EFFECT OF ETHYLENE AND OF STOVE GAS UPON RESPIRATION OF 
LEMONS 
The experiments showing that coloration was prevented or interfered 
with by high and low temperatures and by high concentrations of 
ethylene, that it was favored by intermediate temperatures, and required 
oxygen, indicated that coloring was hastened by conditions that were 
favorable to the life processes of the fruit. Furthermore, whenever ethy¬ 
lene or stove gas was used, coloration was accompanied by the loss or loos¬ 
ening of the buttons (calyx and a portion of the clipped fruit stem). The 
cells at the absciss layer were greatly increased in size, that is, growth and 
enlargement had taken place. In many cases there was an extrusion of 
tissue just below the buttons, a condition similar to that described by 
Doubt (6) and others. If ethylene and stove gas induce coloration by a 
stimulation of the growth of the cells, or by increasing their life activity, 
the respiration of the treated fruit should be increased.' 
Ethylene in concentrations of 1 to 1,000 and 1 to 1,000,000 markedly 
increased the carbon dioxid output, the percentage increases ranging 
from 100 per cent to about 250 per cent. 3 A comparison was made of 
the effect of ethylene and of stove gas upon the respiration of lemons. 
Six lemons, placed in each of six desiccators, received the following 
treatment: 
Lots A and B .—A current of stove gas was drawn through the desic¬ 
cators for six hours each day. The desiccators were then closed and 
placed in an incubator at 25 0 C. until half past 8 o'clock the following 
morning. 
Lot C .—Ethylene to make a concentration of 1 to 10,000 was added 
twice each day, after thorough aeration in outdoor air. The desiccator 
was then placed in the incubator simultaneously with lots A and B. 
3 Denny, F. E. the effect of ethylene upon the respiration of lemons. In Bot. Gaz. Not 
yet published. 
