1914] ATWOOD—GERMINATION OF AVENA 409 
enzyme content in the cells neighboring a wound occurs as a resylt 
of the action of oxygen on the reserve proteins. LEHMANN (49) 
believes germination stimuli are effective through their influence 
on protein hydrolysis. “The work of Miss EckERSON and of GREEN 
Suggests the possibility that the development of acidity leads to 
the liberation of enzymes. What relationship, if any, there may 
be between acidity, oxygen, enzymes, and germinating power in 
A. fatua is worthy of further investigation. 
The character of the changes in the seed of A. fatua with 
after-ripening remains to be discovered. 
Oxygen being considered the limiting factor to germination 
for the freshly harvested seed, it is possible to consider that the 
embryo in the course of after-ripening either decreases in its 
demands for oxygen, whereby the seeds become able to grow in 
gases poor in oxygen; or we may suppose that there is no decrease 
in oxygen demands, but rather an increased permeability of the 
coat'to oxygen. The fact that after-ripened seeds can grow better 
than fresh seeds in chambers poor in oxygen, although the former 
regularly absorb oxygen at a more rapid rate in respiration under 
normal conditions, together with the results (as shown graphically 
in fig. 13) that fresh and after-ripened seeds in the presence of high 
percentages of oxygen absorb at similar rates, seem to favor, but 
not to prove, the general idea that the coat exclusion to oxygen be- 
comes less complete as the seed after-ripens. What mechanism is 
released by the greater oxygen supplied either artificially through 
breaking the coat, or submitting the seed to high percentages of 
oxygen, or under natural conditions through a slowly developed in- 
crease in the coat’s permeability to oxygen, is as yet an open 
question. If further investigation upholds the data given above, 
showing an increased acidity of the embryo with after-ripening, 
we must recognize the fact that in A. fatwa after-ripening involves, 
in addition to physical changes of the coat, accompanying chemical 
alterations of the embryo itself. 
IV. Summary 
- 1. The germination of A. fatwa has been found less delayed 
with the shell coats removed from the seed. However, with the 
shell coats removed, there exist after harvest germinative delays 
