388 BOTANICAL GAZETTE [NOVEMBER 
amount of oxgyen necessary for germination with the coats removed. 
TAKAHASHI has shown that rice germinates in total absence of free oxygen, 
and CrocKER® has shown the same to be true for Alisma Plantago and 
Eichhornia. But the seeds of Xanthium with coats removed remain dor- 
mant if oxygen is ey excluded, though all other germinative conditions 
are supplied. 
The oxygen pressure necessary for the germination of seeds of X. penn- 
sylvanicum has been determined with apparatus similar to that used by 
ScCHAIBLE,7? with modifications to exclude light and to control the tempera- 
ture. The seeds are soaked in ice water for twelve hours, and the coats 
carefully removed, thus excluding them as a factor. The temperature was 
uncontrolled during the first experiments, but it was found immediately 
that high temperatures would yield results differing from those at low tem- 
peratures. The jars, therefore, were kept in a water bath with cold water 
running through it constantly. The variation in temperature was not 
more than about two degrees during the time of each experiment. The 
seeds used at pressures of less than 99™™ of mercury were collected in the 
spring, after lying in the field nearly six months. Those at 99™™ and above 
were collected in the fall as soon as ripe, and were kept in an unheated dry 
room during the winter and succeeding spring. Each lot of seeds was put 
on wet absorbent cotton and was subjected to certain conditions of pressure 
for ten days. The elongation of the hypocotyl, followed by the geotropic 
response, was used as a criterion of germination. 
Since the desired oxygen pressure is secured by a reduction of total 
atmospheric pressure, the question naturally arises whether the - reduction 
of pressure itself has any influence on the germination. Experiments are 
being conducted using the same oxygen pressures at full atmospheric pres- 
sure to determine whether the mere difference in pressure is a factor. As 
some time must elapse before these can be continued, I present the results 
of the first series of experiments in the accompanying table. 
The effect of high temperature is seen by comparing the two experiments 
at 72™™_ The experiment at 99™™ was conducted with seeds that had been 
kept in the laboratory over winter, and the temperature averaged nearly 
2° lower than the one at 90™™, so that the percentage of germination was 
slightly less than at 90™™, in spite of the increased oxygen pressure. 
s TAKAHASHI, T., Is germination possible in absence of air? Bull. Coll. Agr- 
Tokyo 6:439-442. 1905. 
6 CROCKER, WILLIAM, Longevity of seeds. Bot. GAZETTE 47:69-72. 1909- 
7 SCHAIBLE, FR., Physiologische Experimente iiber das Wachstum und die Keimung, 
einiger Pflanzen unter vermindertem Luftdruck. Beitrage Wiss. Bot. 4293-148. 1900- 
