BRIEFER ARITPCLEs 
OXYGEN PRESSURE AND THE GERMINATION OF 
XANTHIUM SEEDS 
A PRELIMINARY REPORT 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 130 
Progress in the analysis of the conditions which cause delayed germina- 
tion in seeds has been disappointingly slow, largely due to the fact that 
investigators have persisted in neglecting the seed coat as a factor on account 
of its thinness, as in K1nzE1’s recent paper,! or because of a preconceived 
idea that the embryonic protoplasm is more or less dormant in newly ripened 
seeds, as in FiscHER’s work,? and that some stimulus is necessary to acti- 
vate it. 
It has been shown by CRocKER3 that the seed coat of Xanthium, in 
spite of its thinness, is the sole cause of delay under normal germinative 
conditions. He has also shown‘ that the delayed germination in seeds of 
aquatic plants depends in many instances on the seed coats. It is evident 
that the testa cannot be neglected as a factor until its insignificance in that 
role has been proven. If seeds are tested with coats removed, it is possible 
that no dormant protoplasm will be found needing ionic or other stimulus 
to growth. Investigations in which the seed coat has been arbitrarily neg- 
lected for any reason will have to be repeated before a satisfactory inter- 
pretation can be attempted. 
On the other hand, it is certain that there are cases in which the delay 
must be attributed to protoplasmic characters, as in Crataegus, the testa of 
Whose seeds has been proven not to be the cause of the delay in germina- 
tion. The conditions for protoplasmic activity in the embryo of plants 
have not been analyzed carefully. A series of experiments is being con- 
ducted with the seeds of Xanthium pennsylvanicum to determine the exact 
‘ KInzEL, Wi1HELM, Lichtkeimung. Einige bestitigende und ona 
Bemerkungen zu den vorliufigen Mittheilungen von 1907 und 1908. Ber. Deuts 
Bot. Gesells. 26a: 631-645. 1908. 
2 Fis , ALFRED, Wasserstoff und Hydroxylionen als Keimungsreize. Ber. 
Deutsch. Bot ‘beee 25 :108-122. 1907. 
3 CROCKER, WILLIAM, Réle of seed coats in delayed germination. Bot. GAZETTE 
42:265-291. 1906 
# , Germination of seeds of water plants. Bot, GAZETTE 44:375-380. 1907. 
387) [Botanical Gazette, vol. 48 
