~ 1914] ATWOOD—GERMINATION OF AVENA 399 
directly. The gas used was generated electrolytically by the 
American Oxhydric Company of Milwaukee, and showed high 
percentage of purity on analysis. Considering the air check as 20 
per cent oxygen, tests were made at the further percentages of 2, 
4, 8, 16, 40, 60, 80, and approximately pure oxygen. Comparing 
the effect of reduced oxygen content on the germination of both 
intact and seared seeds of A. fatwa, greater ability is noticed for 
the seared seeds to grow with good percentages in concentrations 
of one-fifth the normal oxygen during December (fig. 3). 
For April and May, if we compare the sound and seared seeds 
of A. fatua and A: sativa as shown in fig. 4, it is evident that searing 
increases the germination of both at all percentages of oxygen, the 
difference caused by searing being greater for the wild oat. The 
tame oat shows a high germination rate even in very low concen- 
trations of oxygen. If we follow the intact wild oat through the 
winter, there is a noticeable rise in the ability of the seed to grow 
at lowered oxygen concentrations (fig. 5). If, on the other hand, 
increased concentrations of oxygen be tried upon A. fatwa through 
_ the after-ripening period, there is noticeable a larger percentage of 
germination with increased oxygen concentrations up to about 60 
per cent, beyond which point the seedlings tend to become stunted. 
The rise in viability from December to May is also noticeable 
eS es 
6. MEASUREMENTS OF OXYGEN ABSORPTION.—The above results 
with variations in the oxygen concentration and in the season of 
the year may indicate either that as the season progresses there is 
a decrease in the embryo requirements for oxygen necessary to 
secure germination, or that there are modifications taking place 
in the seed by which the entry of oxygen may be more easily accom- 
plished. To determine the nature of the rates of absolute oxygen 
absorption under these varying conditions, and as compared with 
A. sativa, a modification of the eudiometer, as devised by CROCKER, 
was employed (fig. 7). Seven seeds were used in each chamber. 
They were weighed to 0.1 mg., and moisture content determined 
in other seeds from the same lot, from which data the dry weight 
of the seeds used was computed. Before setting up the apparatus, 
the seeds were soaked over night in distilled water in the ice chest. 
