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The Different Forms of Flowers on Plants of the Same Species by Charles Darwin
page 10 of 371 (02%)
powder, and in the case of Pyrethrum, M. Belhomme has shown that the ray-florets
are more poisonous than the disc-florets in the ratio of about three to two. We
may therefore believe that the ray-florets are useful in protecting the flowers
from being gnawed by insects. (Introduction/9. 'Gardener's Chronicle' 1861 page
1067. Lindley 'Vegetable Kingdom' on Chrysanthemum 1853 page 706. Kerner in his
interesting essay 'Die Schutzmittel der Bluthen gegen unberufene Gaste' 1875
page 19, insists that the petals of most plants contain matter which is
offensive to insects, so that they are seldom gnawed, and thus the organs of
fructification are protected. My grandfather in 1790 'Loves of the Plants' canto
3 note to lines 184, 188, remarks that "The flowers or petals of plants are
perhaps in general more acrid than their leaves; hence they are much seldomer
eaten by insects.")

It is a well-known yet remarkable fact that the circumferential flowers of many
of the foregoing plants have both their male and female reproductive organs
aborted, as with the Hydrangea, Viburnum and certain Compositae; or the male
organs alone are aborted, as in many Compositae. Between the sexless, female and
hermaphrodite states of these latter flowers, the finest gradations may be
traced, as Hildebrand has shown. (Introduction/10. 'Ueber die
Geschlechtsverhaltnisse bei den Compositen' 1869 pages 78-91.) He also shows
that there is a close relation between the size of the corolla in the ray-
florets and the degree of abortion in their reproductive organs. As we have good
reason to believe that these florets are highly serviceable to the plants which
possess them, more especially by rendering the flower-heads conspicuous to
insects, it is a natural inference that their corollas have been increased in
size for this special purpose; and that their development has subsequently led,
through the principle of compensation or balancement, to the more or less
complete reduction of the reproductive organs. But an opposite view may be
maintained, namely, that the reproductive organs first began to fail, as often
happens under cultivation, and, as a consequence, the corolla became, through
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