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
In order to judge of the degree of inferiority in fertility of the several
illegitimate plants, the following statement of the average and of the maximum
number of seeds produced by ordinary or legitimate plants, when legitimately
fertilised, some artificially and some naturally, will serve as a standard of
comparison, and may in each case be referred to. But I give under each
experiment the percentage of seeds produced by the illegitimate plants, in
comparison with the standard legitimate number of the same form. For instance,
ten capsules from the illegitimate long-styled plant (Number 10), which was
legitimately and naturally fertilised by other illegitimate plants, contained on
an average 44.2 seeds; whereas the capsules on legitimate long-styled plants,
legitimately and naturally fertilised by other legitimate plants, contained on
an average 93 seeds. Therefore this illegitimate plant yielded only 47 per cent
of the full and normal complement of seeds.
STANDARD NUMBER OF SEEDS PRODUCED BY LEGITIMATE PLANTS OF THE THREE FORMS, WHEN
LEGITIMATELY FERTILISED.
Long-styled form:
Average number of seeds in each capsule, 93;
Maximum number observed out of twenty-three capsules, 159.
Mid-styled form:
Average number of seeds, 130;
Maximum number observed out of thirty-one capsules, 151.
Short-styled form:
Average number of seeds, 83.5; but we may, for the sake of brevity, say 83;
Maximum number observed out of twenty-five capsules, 112.
CLASSES 1 AND 2. ILLEGITIMATE PLANTS RAISED FROM LONG-STYLED PARENTS FERTILISED
WITH POLLEN FROM THE MID-LENGTH OR THE SHORTEST STAMENS OF OTHER PLANTS OF THE
SAME FORM.
From this union I raised at different times three lots of illegitimate
seedlings, amounting altogether to 56 plants. I must premise that, from not
foreseeing the result, I did not keep a memorandum whether the eight plants of
the first lot were the product of the mid-length or shortest stamens of the same
form; but I have good reason to believe that they were the product of the
latter. These eight plants were much more dwarfed, and much more sterile than
those in the other two lots. The latter were raised from a long-styled plant
growing quite isolated, and fertilised by the agency of bees with its own
pollen; and it is almost certain, from the relative position of the organs of
fructification, that the stigma under these circumstances would receive pollen
from the mid-length stamens.
Public-domain text, read in full here on John Shaqi.
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