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10
onlj’ tell us with certainty which seeds would be able to germinate,
if the bird in question had been killed in such a way lliat the seeds
would eome free: but it will also tell us with some probability
which seeds will have a chance for dispersal in an endozoic
männer through birds. To get better knowledge concerning this later
point, which is the one of importance, it will be necessary to
make other experiments. A. Kerner (8) has fed birds with seeds,
taken the unhurt seeds from the excreinents and tested their
germinating power. Charles Darwin (3) has examined the
excre-ments of birds found in bis garden for seeds, and lie reports to
have found 12 kinds of seeds, of which some germinated. This
later way is the möre natural one, but it has the fault that one
does not know the species of birds from which the excrement in
question came; further it is a somewliat occasional way which
will not give exhaustive results.
The author has happened in Unding once the excrements of
some water-bird, probably Anas boschas, containing a lot of seeds
of Potamogeton natans. Next year Mr. Ove Rostrup placed at bis
disposal excrements of swans (Cygiuis olor) stutl’ed with seeds of
Potamogeton natans just in the same männer. The author then
collected material of ripen Potamogeton-seeds at the same place
from where the swan-excrements came and began an experiment to
clear up the ell’ect of the passing through the digestive apparatus
of a swan.
Roth kinds of seeds were kept dry during a month, and then
four glass-vessels were filled with water to a height of about 10
cm.; in each vessel 100 seeds were dropped; in two vessels the
swan-seeds» the seeds laken from swan-excrements) were placed,
in two others the untouched seeds. The »swan-seeds» consist of
the bard endocarp and the embryo, while Ihe untouched seeds
l’ur-ther have a lleshy exocarp outside. A couple of vessels consisting
of one with »swan-seeds» and one with untouched seeds was placed
during the winter close to the heating apparatus of a room; the
other couple slood between the double panes of a window and was
frozen at least from Decemb. 2<Sth to Jan. 5th.
The table ön p. 6 gives the result of the experiment. It becomes
evident that the effect of Ihe digestion has been in favour of
the germination. The »swan-seeds» germinate better and
faster than the untouched seeds.
The author then discusses the männer in which Ulis effect has
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