But we should bear in mind that the trial was not quite fair, as
the self-fertilised plants had a great advantage over the crossed in
being much less crowded in their own row, owing to the large number of
seeds which had perished under ground after sprouting. Nor were the lots
in the two rows subjected to any mutual competition.
29. CANNACEAE.--Canna warscewiczi.
In most or all the species belonging to this genus, the pollen is shed
before the flower expands, and adheres in a mass to the foliaceous
pistil close beneath the stigmatic surface. As the edge of this mass
generally touches the edge of the stigma, and as it was ascertained by
trials purposely made that a very few pollen-grains suffice for
fertilisation, the present species and probably all the others of the
genus are highly self-fertile. Exceptions occasionally occur in which,
from the stamen being slightly shorter than usual, the pollen is
deposited a little beneath the stigmatic surface, and such flowers drop
off unimpregnated unless they are artificially fertilised. Sometimes,
though rarely, the stamen is a little longer than usual, and then the
whole stigmatic surface gets thickly covered with pollen. As some pollen
is generally deposited in contact with the edge of the stigma, certain
authors have concluded that the flowers are invariably self-fertilised.
This is an extraordinary conclusion, for it implies that a great amount
of pollen is produced for no purpose.
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