1909] BRIEFER ARTICLES 389 
It is perfectly clear from the figures given that the oxygen pressure neces- 
sary for germination is quite low, and that the pressure is not the same for 
the two seeds. The uppers require a higher pressure than the lowers; this 
is a real physiologic difference between the two seeds. It must be noticed 
that the difference in the embryo in the two seeds is in the same direction 
as the difference in their seed coats, both sets of characters acting in conjunc- 
tion, not in opposition, in causing a longer delay in the uppers than in the 
lowers. However, the difference is so slight in the embryonic characters 
that the germination of the uppers is not at all hindered if the seed coats are 
off, with full atmospheric pressure. The uppers begin to germinate on the 
average just a few hours later than the lowers under such conditions. 
PERCENTAGE GERM. IN | GROWTH IN LENGTH OF HY- 
Io DAYS POCOTYL IN 10 DAYS (MM) 
MOS- OXYGEN 
A eaaeel PRESSURE ‘TEMPERATURE Z 3 Z 3 2 3 z 3 
PLS | Ble] 6 he pels 
= Qo = Uv = O =) Oo 
9gmm™ 20.72mm 19g—22° 75 | 100 | 45 | 95 | 14-5 | 30-9] 4-9 | 23-3 
9 8.84 21-22.6 | 8 95 | 50 | 100 } 22.8 | 45.9} 4-3} 37-8 
*72 15.07 20-28 45 | 100 | 2 100 | 11.5 |46.0|9-4 | 33.6 
_ 15.07 20-2 30 o | 100 | 6.36} 28.5] 0.0| 22.0 
*28 5.86 2I.5-24.5 o| 100} o| 95 | 00.0 | 37.8] 0.0} 28.8 
*® Temperat + trolled, 
The seeds which failed to germinate under the experimental conditions 
of pressure and moisture were in every case brought into normal germinating 
conditions at the close of each experiment. Germination of roo per cent. 
in nearly every instance shows that the seeds are not injured by the experi- 
mental conditions. 
The surprising feature of the results is the small amount of oxygen pres- 
sure necessary for germination. From the rapid exchange of gases which 
Crocker has shown takes place in the seeds of the cocklebur, one would 
expect to find a rather high pressure required. The results I have obtained 
are inconsistent with the rapid respiration which he has shown to occur. 
Two things must be taken into consideration in regard to this apparent 
4 contradiction of results. In the first place, the seed coats are probably 
_ fesponsible for a large amount of the respiration observed in the seeds of 
Xanthium with the coats intact. BECQUEREL® has shown that the integu- 
ments of seeds produce CO? quite freely, often showing a larger output than 
the seeds from which they are taken. 
= 8 BECQUEREL, Paut, Recherches sur la vie latente de graines. Ann. Sci. Nat. 
Bot. IX, 5 2 193-320. 190 
