Stoward. — On Endospennic Respiration in Certain Seeds. 437 
the same number of seeds — appears to imply that the isolated embryo 
of this seed respires more actively than does the embryo when forming part 
of the intact seed. That such a result may actually occur finds some 
support from the following considerations : — 
1. When plant-tissues are subjected to injury they manifest (10) 
a ‘ wound reaction ’ the outward expression of which is a marked increase 
in their respiratory activity. 
2. The increased respiratory activity (greater C 0 2 production) of the 
isolated embryo may, in part, depend upon the greater amount of surface 
directly exposed to atmospheric air, thus tending to facilitate the process 
of gaseous diffusion both inwards and outwards, within certain limits. 
Slight wounding of the embryo of Zea during its removal from the 
seed is almost unavoidable, but to what extent both this and the second 
factor influence its respiratory activity must be left for more direct 
experimental investigation. 
The difference in the output of C 0 2 by the endosperms and pure 
endosperms of both these seeds may fairly be attributed to the respiration 
of the aleurone layer. 
Thus, removal of the aleurone layer from the endosperm in both the 
‘ Summer 5 and * Winter’ experiments with Hordeum , and in the experiments 
with Zea, leads to marked fall in the output of C 0 2 , and indicates ap- 
proximately the comparatively large share of the total respiratory output 
that is due to aleurone layer respiration. 
This difference is still more clearly placed in evidence in the following 
table — 
Table. Aleurone Layer Respiration. 
Hordeum. 
Average output 
Mgms. C0 2 . 
Difference = Aleurone 
layer respiration. 
Mgms. C0 2 . 
Endosperms (Summer experiments) . . 
0-07210 
Pure endosperms (Summer experiments) 
0-02012 
0-05198 
Endosperms (Winter experiments) . . 
0-01762 
Pure endosperms (Winter experiments) . 
0-007564 
0-010056 
Zea. 
Endosperms 
0-01421 
Pure endosperms 
0-004819 
0-009391 
12. Non Re-established Experiments. 
Most of the experiments with endosperms and pure endosperms of 
Hordeum , and all of those with Zea , were performed in such a manner that 
the experiment once started was continued during its entire course without 
