the most abnormal in their teeth.
I know of no case better adapted to show the importance of the laws of
correlation in modifying important structures, independently of utility
and, therefore, of natural selection, than that of the difference
between the outer and inner flowers in some Compositous and
Umbelliferous plants. Every one knows the
difference in the ray and central florets of, for instance, the daisy,
and this difference is often accompanied with the abortion of parts of
the flower. But, in some Compositous plants, the seeds also differ in
shape and sculpture; and even the ovary itself, with its accessory
parts, differs, as has been described by Cassini. These differences
have been attributed by some authors to pressure, and the shape of the
seeds in the ray-florets in some Composit countenances this idea; but,
in the case of the corolla of the Umbellifer , it is by no means, as
Dr. Hooker informs me, in species with the densest heads that the inner
and outer flowers most frequently differ. It might have been thought
that the development of the ray-petals by drawing nourishment from
certain other parts of the flower had caused their abortion; but in
some Composit there is a difference in the seeds of the outer and
inner florets without any difference in the corolla. Possibly, these
several differences may be connected with some difference in the flow
of nutriment towards the central and external flowers: we know, at
least, that in irregular flowers, those nearest to the axis are
oftenest subject to peloria, and become regular. I may add, as an
instance of this, and of a striking case of correlation, that I have
recently observed in some garden pelargoniums, that the central flower
of the truss often loses the patches of darker colour in the two upper
petals; and that when this occurs, the adherent nectary is quite
aborted; when the colour is absent from only one of the two upper
petals, the nectary is only much shortened.
With respect to the difference in the corolla of the central and
exterior flowers of a head or umbel, I do not feel at all sure that C.
C. Sprengel s idea that the ray-florets serve to attract insects, whose
agency is highly advantageous in the fertilisation of plants of
these two orders, is so far-fetched, as it may at first appear: and if
it be advantageous, natural selection may have come into play. But in
regard to the differences both in the internal and external structure
of the seeds, which are not always correlated with any differences in
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