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
projected above the anthers, but neither were properly long-styled or equal-
styled; and in the one in which the stigma projected most, the grains were in
diameter to those in the other plant, in which the stigma projected less, as 100
to 88; whereas the difference between the grains from perfectly characterised
long-styled and short-styled plants is as 100 to 57. So that these two plants
were in an intermediate condition. To return to the 17 plants in the first line
of Table 5.31: from the relative position of their stigmas and anthers, they
could hardly fail to fertilise themselves; and accordingly four of them
spontaneously yielded no less than 180 capsules; of these Mr. Horwood selected
eight fine capsules for sowing; and they included on an average 54.8 seeds, with
a maximum of 72. He gave me thirty other capsules, taken by hazard, of which
twenty-seven contained good seeds, averaging 35.5, with a maximum of 70; but if
six poor capsules, each with less than 13 seeds, be excluded, the average rises
to 42.5. These are higher numbers than could be expected from either well-
characterised form if self-fertilised; and this high degree of fertility accords
with the view that the male organs belonged to one form, and the female organs
partially to the other form; so that a self-union in the case of the equal-
styled variety is in fact a legitimate union.
The seed saved from the above seventeen self-fertilised equal-styled plants
produced sixteen plants, which all proved equal-styled, and resembled their
parents in all the above-specified respects. The stamens, however, in one plant
were seated higher up the tube of the corolla than in the true long-styled form;
in another plant almost all the anthers were contabescent. These sixteen plants
were the grandchildren of the four original plants, which it is believed were
equal-styled; so that this abnormal condition was faithfully transmitted,
probably through three, and certainly through two generations. The fertility of
one of these grandchildren was carefully observed: six flowers were fertilised
with pollen from the same flower, and produced six capsules, containing on an
average 68 seeds, with a maximum of 82, and a minimum of 40. Thirteen capsules
spontaneously self-fertilised yielded an average of 53.2 seeds, with the
astonishing maximum in one of 97 seeds. In no legitimate union has so high an
average as 68 seeds been observed by me, or nearly so high a maximum as 82 and
97. These plants, therefore, not only have lost their proper heterostyled
structure and peculiar functional powers, but have acquired an abnormal grade of
fertility--unless, indeed, their high fertility may be accounted for by the
stigmas receiving pollen from the circumjacent anthers at exactly the most
favourable period.
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Elsewhere in the archive
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account