406 ; BOTANICAL GAZETTE [MAY 
higher concentrations is shown. This increase is least noticeable 
in the case of the high percentage of oxygen tests. It is suggested 
that if coat restrictions are concerned, and if their effects are over- 
come by high concentrations of oxygen, the four curves would 
tend to come together, as is found to be the case. 
Summarizing the 
~30 ug ‘ 
respiration tests, it 
would seem that asso- 
eA ciated with increased 
7 germinative rates 
= /| accompanying after- 
7 ripening there is an in- 
4 < creased ability of the 
ac Pet seed to take up oxygen, 
ie 7 was providing always that 
the conditions of germi- 
~ —-—— 
: os nation be the same; and, 
45 further, that wounding 
and subjecting to in- 
creased oxygen con- 
centrations actually 
- increases the oxygen in- 
take. Nevertheless, the 
process of after-ripening 
may not consist pri- 
mils} ; ‘ n ° 
marily in an increased 
: 10 Hours 30 5 
) 
Fic. 12.—Rates of oxygen ab tion f a 
wild oats before and subsequent to aiter-ripening in 
terms of cc. per hour per gm. dry weight; rates in 
winter, solid line; in spring, broken line. freed from limitations to 
absorption, as was ac 
complished in the experiments summarized in fig. 12, it is apparent 
that their oxygen-absorption rate closely approximates that of the 
seeds which have thoroughly after-ripened. Thus the changes, 
whether they be seed coat or embryonal, which we ordinarily term 
after-ripening, and which are exhibited by increased rate of oxyge 
intake, may be immediately attained by artificially overcoming 
