The Different Forms of Flowers on Plants of the Same SpeciesDarwin, Charles
Science
The Different Forms of Flowers on Plants of the Same Species
Darwin, Charles
Fertilization of plants; Heterostylism; Plant physiology; Plants -- Variation; Pollination
As bearing on inheritance, it may be added that 72 seedlings were raised from
one of the red-flowered, strictly equal-styled, self-fertilised plants descended
from the similarly characterised Edinburgh plant. These 72 plants were therefore
grandchildren of the Edinburgh plant, and they all bore, as in the first
generation, red flowers, with the exception of one plant, which reverted in
colour to the common cowslip. In regard to structure, nine plants were truly
long-styled and had their stamens seated low down in the corolla in the proper
position; the remaining 63 plants were equal-styled, though the stigma in about
a dozen of them stood a little below the anthers. We thus see that the anomalous
combination in the same flower, of the male and female sexual organs which
properly exist in the two distinct forms, was inherited with much force. Thirty-
six seedlings were also raised from long and short-styled common cowslips,
crossed with pollen from the equal-styled variety. Of these plants one alone was
equal-styled, 20 were short-styled, but with the pistil in three of them rather
too long, and the remaining 15 were long-styled. In this case we have an
illustration of the difference between simple inheritance and prepotency of
transmission; for the equal-styled variety, when self-fertilised, transmits its
character, as we have just seen, with much force, but when crossed with the
common cowslip cannot withstand the greater power of transmission of the latter.
PULMONARIA.
I have little to say on this genus. I obtained seeds of P. officinalis from a
garden where the long-styled form alone grew, and raised 11 seedlings, which
were all long-styled. These plants were named for me by Dr. Hooker. They
differed, as has been shown, from the plants belonging to this species which in
Germany were experimented on by Hildebrand (5/13. ‘Botanische Zeitung’ 1865 page
13.); for he found that the long-styled form was absolutely sterile with its own
pollen, whilst my long-styled seedlings and the parent-plants yielded a fair
supply of seed when self-fertilised. Plants of the long-styled form of
Pulmonaria angustifolia were, like Hildebrand’s plants, absolutely sterile with
their own pollen, so that I could never procure a single seed. On the other
hand, the short-styled plants of this species, differently from those of P.
officinalis, were fertile with their own pollen in a quite remarkable degree for
a heterostyled plant. From seeds carefully self-fertilised I raised 18 plants,
of which 13 proved short-styled and 5 long-styled.
Polygonum fagopyrum.
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