S toward, — On Endospermic Respiration in Certain Seeds. 439 
The maintenance of this more or less constant output further tends to 
strengthen the view that the respiratory exchanges are due to the 
respiratory activity of the material under investigation, and not in part to 
micro-organisms which may have fortuitously gained admission either 
before or during the course of the experiments. 
An objection which may be urged against both types of experiment 
(re- and non re-established) is that no provision was made to ensure 
uniform mixing of the gaseous respiration products before removing the 
specimen for analysis. When, however, it is borne in mind that the total 
volume of the gaseous mixture in these experiments only amounted to 
a few c.cs. it will be evident that, even without the aid of any mechanical 
device to ensure uniform mixing, lack of uniform diffusion could only occur 
in a very restricted sense, if at all. 
14. Effect of Diminished Pressure on Initial 
Output of C0 2 . 
In a number of experiments, the material, just prior to the establish- 
ment of each experiment, was subjected to diminished pressure for a short 
interval of time. 
As the results with endosperms of Hordeum in general show, the effect 
of subjecting material to diminished pressure tends to reduce the initial 
output of C0 2 . The output of C0 2 observed in these experiments as they 
progress, instead of progressively diminishing as in the non re-established 
ones, tends to increase ; so that at the termination of the experiment the 
final is rather larger than the initial output, i. e. the result is a reversal of 
that observed in the non re-established experiments. 
The results also demonstrate that, on the one hand, when the tissue 
is initially depleted of part of its C0 2 , an appreciable time must necessarily 
elapse before this gas again acquires its maximum tension in the tissues ; 
and following on this its normal concentration in the gaseous space outside ; 
while, on the other, they strengthen the evidence already put forward in 
favour of the view that an actual production of C0 2 takes place. 
Not only is the tissue under these circumstances depleted in part of 
its C0 2 , but also of its 0 2 , for in all these experiments the increased 
absorption of 0 2 is a noticeable feature. 
Similar observations apply in the main to those experiments with 
Hordeum in which chloroform-steeped endosperms were initially exposed 
to diminished pressure, although here a small difference is noticeable in the 
initial and final outputs of C0 2 , the final being slightly lower than the 
initial. Yet, if these results are compared with those of chloroform-steeped 
endosperms, not subjected to diminished pressure, it will be seen that the 
final output, relatively to the initial, is lower than in the experiments just 
considered. 
