474 BOTANICAL GAZETTE [DECEMBER 
In CROCKER’S experiments the measurement of the gaseous 
exchange was made for seeds with testas on, and therefore included 
whatever coat CO, production occurred. And, since the thickness 
of the testa over the hypocotyl practically excludes the oxygen 
from that organ, while the thinner distal portion of the coat admits 
the oxygen to the cotyledons first, thus initiating the cotyledonary 
germination mentioned above, the measurement of the gaseous 
exchange has dealt very largely with that occurring in the coty- 
ledons. In my experiments the removal of the coats eliminates 
the coat CO, production; and, since the cotyledons never grow 
under the conditions of the experiment until after the hypocotyl — 
has elongated, the determination of the oxygen minimum is made 
for the hypocotyl only. There is no inconsistency, I believe, 
between the results obtained by Crocker and those obtained in 
these experiments. Indeed, the unusually high minimum for the 
decorticated seeds agrees well with the data secured in earlier 
determinations with the coat intact, when the coat CO, produc- 
tion and the reversal of the correlation between hypocotyl and 
cotyledons are taken into consideration. 
The lowering of the oxygen minimum by increase of temperature 
is at least partially accounted for by the increase in anaerobic 
respiration as the temperature rises. On the other hand, if a 
constant free oxygen supply below the optimum is maintained 
during a rise in temperature, the growth capacity of the organism 
is increased as the temperature rises. It is known, also, that merely 
cutting off the supply of oxygen will increase the anaerobic respira- 
tion in many organisms. With the oxygen reduced to a minimum, 
and at the high temperature employed, the conditions in these 
experiments are favorable to a considerable increase in the anaerobic 
form of respiration. As the anaerobic respiration increases, there 
is less need of the aerobic to release the energy sufficient to initiate 
growth. The question then naturally arises whether the lowering 
of the oxygen minimum by increasing the temperature really 
indicates any difference in the amount of respiration occurring. 
It is possible that the total energy release necessary for the germina- 
tion of the seed is practically the same at any given temperature, 
_ the variation being in the proportion of release due to aerobic 
