Igir] SHULL—OXYGEN MINIMUM AND GERMINATION 465 
but the latter lot was subjected to a temperature 2° lower on the 
average than the former. The results show, instead of an increase 
in percentage of germination and growth in length, as would have 
been expected from the increased supply of oxygen, a decrease of 
5 per cent in the germination of both lowers and uppers, and a 
considerable decrease in the average growth of the lowers in length. 
A number of experiments were performed with the purpose of 
determining how much effect temperature has on the location of 
the minimum. The results are presented here in tabular form. 
For the sake of comparison, one experiment at 72 mm. and room 
temperature is included at the bottom of the table, which may be 
compared with the results at 76 mm. and 31°, and with those at 
75 mm. and 25-40". 
TABLE It 
DURATION OF EXPERIMENTS IO DAYS 
PERCENTAGE OF GROWTH IN LENGTH OF 
Manom- | Vapop | ATMOS- vena B GERMINATION HYPOCOTYL (MM.) 
a : 
s s a 
ancy | Gacy | ER | ood | BLE RIE) BLE BI SE 
%, = c =I a 
| PeTs clele siolete 
Tees 29.0 | 47.0 | 9.8 31 |93.3/100 \40.0 100 |50.4 102.0 32.75)109.0 
no eee 90.2% |. 38.90 | 7-5 31 |60.0/100 |43.3|/100 |33.1 |102.0 20.15/109.0 
ee 99;0 155.6 1 95 31 |80.0/100 |10.0/100 /32.4 | 79.6 24.00) 86.6 
ce eee 25.7 | 30-97). 6.8 31 |66.6)100 | 0.0/T00 |11.6 | 79.6) 0.00) 86.6 
eee Varies) with |temp. |25-40 (93.3) 90 |56.6)100 |37.25 67.4/28.00) 70.6 
ee Varies with |temp. |25-40 |86.6) 90 (26 6\I00 |32.9 | 67.4/17.25| 70.6 
fies pae 16.4 | 55.86) 11.69/20-22 | 30 | 95 | 9.0)/I00 | 6.36 28.5, G16 | 22.0 
The difference between uppers and lowers in percentage of 
germination is even more pronounced at 31° than at 21°, amount- 
ing in some instances to 60 or 70 per cent more germinations among 
the lowers than among the uppers. It appears also from table IT 
that the oxygen minimum is considerably lower at 31° than at 21°, 
especially for the lower seeds. From the data here presented the 
oxygen minima have been approximated by mathematical methods. 
Since a pressure of 65 mm. germinated 10 per cent of the uppers, 
the oxygen minimum as calculated from the results would be about 
6.75 mm. The minimum for the lowers was not accurately deter- 
mined, but at 55 mm. atmospheric pressure, representing an O, 
