1914] SHULL—GERMINATION 69 
did not measure the respiration of the seeds on which they worked. 
However, owing to the complexity of the oxygen réle in physio- 
logical processes, it is very difficult to say just which function or 
functions are affected. It seems certain that the oxygen acts as a 
limiting factor on some function, whether by limiting the process 
of respiration or energy releasal, by limiting enzyme formation 
or the action of oxygen carriers, or in other still less definite ways. 
The exact method by which absence of oxygen delays germination 
can be determined only by further investigation. In the mean- 
time theories may well await the facts which will make philoxephice| 
discussion of this question unnecessary. 
UNIVERSITY oF KANSAS 
LAWRENCE, Kan. 
