476 BOTANICAL GAZETTE [DECEMBER 
6. A very slow progressive deterioration of the seeds takes place, 
which after a few years causes entire loss of power to germinate. 
7. The general conclusion that the organs of the seeds of higher 
plants can grow in entire absence of free oxygen is not supported 
by the results obtained with Xanthium seeds. They cannot grow 
without comparatively large amounts of free oxygen. 
8. The oxygen pressures required for germination of Xanthium 
seeds are very much higher than those reported by LEHMANN for 
the epicotyls of such plants as Helianthus perennis, Zinnia elegans, 
and Glyceria fluitans. 
g. Since the coats cause delay by excluding oxygen, we might 
expect to find the oxygen demand for growth high. Xanthium 
seeds stand at the opposite end of the series from the seeds of certain 
aquatic plants, as water plantain and rice, in demands for oxygen 
for germination. 
10. The high oxygen demand, and the difference in this demand 
in the two seeds, act with the coats to secure delay, and a difference 
in delay, in the two seeds. But if the coat has been removed, the 
demand for oxygen by the embryo is too low to be significant in 
securing delay in germination. 
TRANSYLVANIA UNIVERSITY 
LexrncrTon, Ky. 
LITERATURE CITED 
1. ArTHur, J. C., Delayed germination in the cocklebur and other paired 
seeds. Proc. Soc. Prom. Agric. Sci. 16:70-79. 1895. : 
2. BECQUEREL, Paut, Recherches sur la vie latente des graines. Ann. Scl. 
Nat. Bot. IX. 5:193-320. 1907. 
3- Correns, C., Das Keimen der beiderlei Friichte der Dimorphotheca plu- 
vialis. Ber. Deatich, Bot. Gesells. 24:173-176. 1906. 
4. CROCKER, WILLIAM, 3 of seed coats in delayed germination. Bot. 
GAZ. 42:265-291. 1 
*, of ean gt of the seeds of water plants. Bort. Gaz. 44:375-38°- 
1907. 
6. Ernst, re Das Keimen der dimorphen Fruchten von Synedrella nodt- 
flora (L.) Gris. Ber. Deutsch. Bot. Gesells. 24:450-458. 1906. 
7- Fawcett, H. S., The viability of weed seeds under different conditions of 
treatment, and a study of their dormant periods. Proc. Iowa Acad. Sci. 
PP. 25-45. 1908. 
8. FiscHer, ALFRED, Wasserstoff und Hydroxylionen als Keimungsreize. 
Ber. Deutsch. Bot. Gesells. 25: 108-122. 1907. 
