1906] CROCKER—DELAYVED GERMINATION 281 
Contrary to NopBe AND HANLErIN’s conclusion, the distributed germi- 
nation shown by this species is secured by the slowness with which 
water penetrates the seed coats. 
While in Axyris and Xanthium delayed or distributed germina- 
tion is secured by peculiar seed coat characters of one form of the 
dimorphic seeds, in Abutilon Avicennae and Chenopodium album 
the distributed germination is secured by a variation in the seed 
coat characters of similar seeds. 
4. IRIs. 
Dr. C. J. CHAMBERLAIN informed ‘me that he had never succeeded 
in germinating seeds of various species of Iris, although he had often 
attempted it in order to have root tips for cytological purposes. The 
bulk of the seed consists of the horny endosperm with food stored 
on the walls as hemicellulose. On one side of the endosperm is a 
cylindrical cavity in which the embryo is borne. The cavity is 
covered by a cap, thus entirely closing in the embryo, When the 
seed is dry, the embryo only partially fills the cavity, but after twenty- 
four hours soaking it completely fills it. In this condition, however, 
the seeds will lie for weeks without germinating. If now the caps 
are removed and the seeds still kept in the water, the embryo pro- 
trudes 3~-7™™ within an hour. Seeds with caps removed germinate 
very readily, while those with caps intact do not germinate at all. 
For the effect of removing the cap in Iris sibirica and I, Pseudacorus, 
pie Table IX. Increased oxygen pressure and high temperatures 
with the caps intact did not cause germination. With the caps 
‘moved, the most successful germination was secured by using 
Sterilized sand as a germinator at 28-33°. 
The amount of moisture absorbed by the embryo within the 
miting wall of the endosperm is not sufficient to permit growth to 
egin. By taking away this limit to water absorption by removal 
of the cap or a portion of the endosperm in the region of the embryo, * 
absorption is resumed and growth soon begins. Judging from a 
umber of observations, it appears that in nature long soaking and 
“¢companying disintegration lead to the loosening of the cap, or 
more frequently to the decay of the endosperm at one side of the 
embryo, 
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