The Different Forms of Flowers on Plants of the Same Species | Page 7

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 compensation, more highly developed. (Introduction/11. I have
discussed this subject in my 'Variation of Animals and Plants under

Domestication' chapter 18 2nd edition volume 2 pages 152, 156.) This
view, however, is not probable, for when hermaphrodite plants become
dioecious or gyno-dioecious--that is, are converted into hermaphrodites
and females--the corolla of the female seems to be almost invariably
reduced in size in consequence of the abortion of the male organs. The
difference in the result in these two classes of cases, may perhaps be
accounted for by the matter saved through the abortion of the male
organs in the females of gyno-dioecious and dioecious plants being
directed (as we shall see in a future chapter) to the formation of an
increased supply of seeds; whilst in the case of the exterior florets and
flowers of the plants which we are here considering, such matter is
expended in the development of a conspicuous corolla. Whether in the
present class of cases the corolla was first affected, as seems to me the
more probable view, or the reproductive organs first failed, their states
of development are now firmly correlated. We see this well-illustrated
in Hydrangea and Viburnum; for when these plants are cultivated, the
corollas of both the interior and exterior flowers become largely
developed, and their reproductive organs are aborted.
There is a closely analogous subdivision of plants, including the genus
Muscari (or Feather Hyacinth) and the allied Bellevalia, which bear
both perfect flowers and closed bud-like bodies that never expand. The
latter resemble in this respect cleistogamic flowers, but differ widely
from them in being sterile and conspicuous. Not only the aborted
flower-buds and their peduncles (which are elongated apparently
through the principle of compensation) are brightly coloured, but so is
the upper part of the spike--all, no doubt, for the sake of guiding insects
to the inconspicuous perfect flowers. From such cases as these we may
pass on to certain Labiatae, for instance, Salvia Horminum in which (as
I hear from Mr. Thiselton Dyer) the upper bracts are enlarged and
brightly coloured, no doubt for the same purpose as before, with the
flowers suppressed.
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