In the Carrot and some allied Umbelliferae, the central flower has its petals
somewhat enlarged, and these are of a dark purplish-red tint; but it cannot be
supposed that this one small flower makes the large white umbel at all more
conspicuous to insects. The central flowers are said to be neuter or sterile,
but I obtained by artificial fertilisation a seed (fruit) apparently perfect
from one such flower. (Introduction/12. 'The English Flora' by Sir J.E. Smith
1824 volume 2 page 39.) Occasionally two or three of the flowers next to the
central one are similarly characterised; and according to Vaucher "cette
singuliere degeneration s'etend quelquefois a l'ombelle entiere."
(Introduction/13. 'Hist. Phys. des Plantes d'Europe' 1841 tome 2 page 614. On
the Echinophora page 627.) That the modified central flower is of no functional
importance to the plant is almost certain. It may perhaps be a remnant of a
former and ancient condition of the species, when one flower alone, the central
one, was female and yielded seeds, as in the Umbelliferous genus Echinophora.
There is nothing surprising in the central flower tending to retain its former
condition longer than the others; for when irregular flowers become regular or
peloric, they are apt to be central; and such peloric flowers apparently owe
their origin either to arrested development--that is, to the preservation of an
early stage of development--or to reversion. Central and perfectly developed
flowers in not a few plants in their normal condition (for instance, the common
Rue and Adoxa) differ slightly in structure, as in the number of the parts, from
the other flowers on the same plant. All such cases seem connected with the fact
of the bud which stands at the end of the shoot being better nourished than the
others, as it receives the most sap. (Introduction/14. This whole subject,
including pelorism, has been discussed, and references given in my 'Variation of
Animals and Plants under Domestication' chapter 26 2nd edition volume 2 page
338.)

The cases hitherto mentioned relate to hermaphrodite species which bear