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
This, the one long-styled plant of the same parentage as the last three plants,
when freely and legitimately fertilised in the same manner as the last, yielded
an average from ten capsules of 76.3 rather poor seeds, with a maximum of 88 and
a minimum of 57. Hence this plant produced 82 per cent of the proper number of
seeds. Twelve flowers enclosed in a net were artificially and legitimately
fertilised with pollen from a legitimate short-styled plant; and nine capsules
yielded an average of 82.5 seeds, with a maximum of 98 and a minimum of 51; so
that its fertility was increased by the action of pollen from a legitimate
plant, but still did not reach the normal standard.]
CLASS 4. ILLEGITIMATE PLANTS RAISED FROM A MID-STYLED PARENT FERTILISED WITH
POLLEN FROM OWN-FORM LONGEST STAMENS.
After two trials, I succeeded in raising only four plants from this illegitimate
union. These proved to be three mid-styled and one long-styled; but from so
small a number we can hardly judge of the tendency in mid-styled plants when
self-fertilised to reproduce the same form. These four plants never attained
their full and normal height; the long-styled plant had several of its anthers
contabescent.
[PLANT 18.
This mid-styled plant, when freely and legitimately fertilised during 1865 by
illegitimate plants descended from self-fertilised long-, short-, and mid-styled
plants, yielded an average from ten capsules of 102.6 seeds, with a maximum of
131 and a minimum of 63: hence this plant did not produce quite 80 per cent of
the normal number of seeds. Twelve flowers were artificially and legitimately
fertilised with pollen from a legitimate long-styled plant, and yielded from
nine capsules an average of 116.1 seeds, which were finer than in the previous
case, with a maximum of 135 and a minimum of 75; so that, as with Plant 17,
pollen from a legitimate plant increased the fertility, but did not bring it up
to the full standard.
PLANT 19.
This mid-styled plant, fertilised in the same manner and at the same period as
the last, yielded an average from ten capsules of 73.4 seeds, with a maximum of
87 and a minimum of 64: hence this plant produced only 56 per cent of the full
number of seeds. Thirteen flowers were artificially and legitimately fertilised
with pollen from a legitimate long-styled plant, and yielded ten capsules with
an average of 95.6 seeds; so that the application of pollen from a legitimate
plant added, as in the two previous cases, to the fertility, but did not bring
it up to the proper standard.
PLANT 20.
This long-styled plant, of the same parentage with the two last mid-styled
plants, and freely fertilised in the same manner, yielded an average from ten
capsules of 69.6 seeds, with a maximum of 83 and a minimum of 52: hence this
plant produced 75 per cent of the full number of seeds.]
CLASS 5. ILLEGITIMATE PLANTS RAISED FROM A SHORT-STYLED PARENT FERTILISED WITH
POLLEN FROM THE MID-LENGTH STAMENS OF THE LONG-STYLED FORM.
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