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
Thirty long-styled flowers fertilised illegitimately by their own-form two sets
of stamens yielded only eight very poor capsules; but long-styled flowers
fertilised by bees with pollen from their own stamens produced numerous capsules
containing on an average 21.5 seeds.
MID-STYLED FORM.
Twenty-four flowers legitimately fertilised by the stamens of corresponding
length, borne by the long and short-styled forms, yielded 96 (probably 100) per
cent of capsules, which contained (excluding one capsule with 12 seeds) on an
average 117.2 seeds.
Fifteen mid-styled flowers fertilised illegitimately by the longest stamens of
the short-styled form yielded 93 per cent of capsules, which (excluding four
capsules with less than 20 seeds) contained on an average 102.8 seeds.
Thirteen mid-styled flowers fertilised illegitimately by the mid-length stamens
of the long-styled form yielded 54 per cent of capsules, which (excluding one
with 19 seeds) contained on an average 60.2 seeds.
Twelve mid-styled flowers fertilised illegitimately by their own-form longest
stamens yielded 25 per cent of capsules, which (excluding one with 9 seeds)
contained on an average 77.5 seeds.
Twelve mid-styled flowers fertilised illegitimately by their own-form shortest
stamens yielded not a single capsule.
SHORT-STYLED FORM.
Twenty-five flowers fertilised legitimately by the stamens of corresponding
length, borne by the long and mid-styled forms, yielded 72 per cent of capsules,
which (excluding one capsule with only 9 seeds) contained on an average 70.8
seeds.
Twenty short-styled flowers fertilised illegitimately by the other stamens of
the long and mid-styled forms yielded only two very poor capsules.
Twenty short-styled flowers fertilised illegitimately by their own stamens
yielded only two poor (or perhaps three) capsules.
If we take all six legitimate unions together, and all twelve illegitimate
unions together, we get the following results:
TABLE 4.26.
Column 1: Nature of union.
Column 2: Number of Flowers fertilised.
Column 3: Number of Capsules produced.
Column 4: Average Number of Seeds per Capsule.
Column 5: Average Number of Seeds per Flower fertilised.
The six legitimate unions : 75 : 56 : 96.29 : 71.89.
The twelve illegitimate unions : 146 : 36 : 44.72 : 11.03.
Therefore the fertility of the legitimate unions to that of the illegitimate, as
judged by the proportion of the fertilised flowers which yielded capsules, is as
100 to 33; and judged by the average number of seeds per capsule, as 100 to 46.
Public-domain text, read in full here on John Shaqi.
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