The Effects of Cross & Self-Fertilisation in the Vegetable KingdomDarwin, Charles
Science
The Effects of Cross & Self-Fertilisation in the Vegetable Kingdom
Darwin, Charles
Fertilization of plants; Plants -- Variation; Pollination
Seeds collected from wild plants growing in this neighbourhood were sown
in the kitchen-garden; and several of the seedlings thus raised were
covered with a net. Of these, some were found (as will hereafter be more
fully described) to be absolutely sterile when left to fertilise
themselves spontaneously, although plenty of pollen fell on their
stigmas; and they were equally sterile when artificially and repeatedly
fertilised with their own pollen; whilst other plants produced a few
spontaneously self-fertilised capsules. The remaining plants were left
uncovered, and as pollen was carried from plant to plant by the hive and
humble-bees which incessantly visit the flowers, they produced an
abundance of capsules. Of the necessity of pollen being carried from one
plant to another, I had ample evidence in the case of this species and
of R. odorata; for those plants, which set no seeds or very few as long
as they were protected from insects, became loaded with capsules
immediately that they were uncovered.
Seeds from the flowers spontaneously self-fertilised under the net, and
from flowers naturally crossed by the bees, were sown on opposite sides
of five large pots. The seedlings were thinned as soon as they appeared
above ground, so that an equal number were left on the two sides. After
a time the pots were plunged into the open ground. The same number of
plants of crossed and self-fertilised parentage were measured up to the
summits of their flower-stems, with the result given in Table 4/35.
Those which did not produce flower-stems were not measured.
TABLE 4/35. Reseda lutea, in pots.
Heights of plants to the summits of the flower-stems measured in inches.
Column 1: Number (Name) of Pot.
Column 2: Crossed Plants.
Column 3: Self-fertilised Plants.
Pot 1 : 21 : 12 7/8.
Pot 1 : 14 2/8 : 16.
Pot 1 : 19 1/8 : 11 7/8.
Pot 1 : 7 : 15 2/8.
Pot 1 : 15 1/8 : 19 1/8.
Pot 2 : 20 4/8 : 12 4/8.
Pot 2 : 17 3/8 : 16 2/8.
Pot 2 : 23 7/8 : 16 2/8.
Pot 2 : 17 1/8 : 13 3/8.
Pot 2 : 20 6/8 : 13 5/8.
Pot 3 : 16 1/8 : 14 4/8.
Pot 3 : 17 6/8 : 19 4/8.
Pot 3 : 16 2/8 : 20 7/8.
Pot 3 : 10 : 7 7/8.
Pot 3 : 10 : 17 6/8.
Pot 4 : 22 1/8 : 9.
Pot 4 : 19 : 11 4/8.
Pot 4 : 18 7/8 : 11.
Pot 4 : 16 4/8 : 16.
Pot 4 : 19 2/8 : 16 3/8.
Pot 5 : 25 2/8 : 14 6/8.
Pot 5 : 22 : 16.
Pot 5 : 8 6/8 : 14 3/8.
Pot 5 : 14 2/8 : 14 2/8.
Total : 412.25 : 350.86.
The average height of the twenty-four crossed plants is here 17.17
inches, and that of the same number of self-fertilised plants 14.61; or
as 100 to 85. Of the crossed plants all but five flowered, whilst
several of the self-fertilised did not do so. The above pairs, whilst
still in flower, but with some capsules already formed, were afterwards
cut down and weighed. The crossed weighed 90.5 ounces; and an equal
number of the self-fertilised only 19 ounces, or as 100 to 21; and this
is an astonishing difference.
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