process in other fruits. With the pineapple, we observed
no respiratory rise but our experiments were
too few to be conclusive.
The last column in table I was designed to be used
for comparing the ethylene activity values in relation
to the respiratory capacities of the various fruits.
Generally a low rate of CO2 production is associated
with low or no ethylene evolution. The McIntosh
apple is a notable exception with an unusually high
rate of ethylene evolution. Our findings with this
variety agree with those of Nelson (16). There seems
to be also some correlation between high rates of
ethylene production and high rates of respiration. Of
the fruits which produce ethylene the banana is the
only exception to this direct correlation. It is interesting
to note that the temperate zone fruits show a
high ethylene to CO2 ratio. Our results for Bartlett
pears correspond closely with those of Hansen (8),
who used the micro-bromination method. Compared
to the Bartlett, the rate of ethylene evolution of the
Bose pear was reduced to about the same extent as
the rate of respiration. It would be of interest to
have data on other varieties and species of temperate
zone fruits. The information available for all the
species reported here suggests, howNever, that the
ethylene-producing mechanism might be affected by
factors which leave the overall respiration intact.