1915] HARVEY—ETHYLENE 2it 
concentrations which are in reality, for example in the case of 
chloroform or ether, thousands of times stronger. Probably most 
of the ether concentrations employed by HEMPEL (11) were many 
times weaker, physiologically, than the ethylene concentrations of 
the above-described experiments. Such an assumption would 
account for the difference between some of her results and those 
reported in this paper. It seems probable that ethylene, also, 
would favor condensation processes if used in ‘““weak”’ or “‘medium”’ 
concentrations. 
In the presence of ethylene the simple soluble substances in- 
crease at the expense of the higher soluble and insoluble forms; 
direct reducing sugars against soluble non-reducing sugars and 
insoluble polysaccharides; amino acids and amids against proteins; 
and probably fatty acids and glycerine against fats, seeing that the 
latter were found to diminish. Accordingly, ethylene appears to 
affect the balance of the general chemical reactions of the plant 
in favor of the simpler substances. The experimental work offers 
no evidence as to whether or not this result is accomplished through 
an acceleration of the hydrolytic as well as through a retardation 
of the condensation processes, since all the substances present in 
the tissue examined (epicotyls) had, within a relatively few hours, 
arrived, in simple translocation forms, from the cotyledons. 
The accumulation of soluble substances in the tissue changes 
the osmotic relations of the cells and may have much to do with 
the observed swelling of plant organs in the presence of ethylene, 
for example in the characteristic “horizontal nutation”’ or “triple 
response” of the pea epicotyl. Also, the observed retardation of 
the rate of elongation may partly be accounted for by the fact that 
the gas interferes with the synthesis of complex substances, that 
is to say, perhaps with tissue formation. 
. Summary 
1. Ethylene was found to be very effective in producing changes 
in the general processes of plant metabolism. 
2. Chemical analyses showed that ethylene caused the simple 
soluble substances to increase at the expense of the higher soluble 
and insoluble forms. 
