Stoward. On Endospermic Respiration in Certain Seeds. 443 
18. The Possible Diffusion of Respiratory Enzymes from the 
Embryo and Aleurone Layer to the Endosperm during 
Steeping or Germination. 
If the view be accepted that the respiration of vegetable tissues is 
partly due to the agency of respiratory enzymes, then the possibility must 
be granted that these bodies may be generated either by the embryo or the 
aleurone layer cells, or. by both, and projected into the endosperm during 
steeping or germination of the intact seeds. 
Certain experiments were performed with Hordeum and Zea which 
would permit this process to freely occur. 
The results of the experiments with the endosperms of Hordeum do 
not lend themselves to ready comparison in this respect, but certain 
experiments [Hordeum, Summer Experiments 9, 10, 11) may be advanced 
to show that removal of the embryo from the steeped seed after o, 6 and 
3 hours respectively leads to no very marked change in the C 0 2 output. 
Similarly in Hordeum (Winter Experiments 15, 12, 14, in the last of which 
the seeds were germinated for 24 hours, and the embryos were excised 
after 3, 48, and 73 hours respectively), although the output is slightly 
higher in the last two experiments, yet it is insufficient to strongly support 
the view that diffusion from the embryo had actually taken place, for the 
results may also be interpreted by assuming that the endosperm in Experi- 
ments 12 and 14 had emerged from its latent stage. 
The results of Winter Experiments 37 and 38 with pure endosperms 
derived from germinated seeds, if compared with those already mentioned, 
or with those of Winter Experiments 34 and 35, do appear to furnish 
evidence of diffusion either from the embryo or aleurone layer cells, or 
both ; for the values obtained for the output of C 0 2 are greater than those 
for the pure endosperm in other experiments, and approach or exceed the 
values obtained with endosperms in Experiments 15 and 12. It is very 
difficult to decide, however, whether these results are due to the diffusion 
of respiratory enzymes, or to the emergence of the tissue from its latent 
period. 
The experimental results with Zea , on the other hand, yield no 
evidence favouring this view of possible respiratory enzyme diffusion from 
the embryo or aleurone cells during steeping or germination. 
CO 0 
19. The Respiratory Quotient (-q-^) 
CO 
The relation -pr— 2 given in the tables of experimental data furnishes 
values which throw some light on the character of the respiration of the 
seed and its component parts, although it must be admitted that the 
H h 
