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
Shortly afterwards one of the crossed plants in Pot 1 died; another
became much diseased and stunted; and the third never grew to its full
height. They seemed to have been all injured, probably by some larva
gnawing their roots. Therefore all the plants on both sides of this pot
were rejected in the subsequent measurements. When the plants were fully
grown they were again measured to the tips of the highest leaves, and
the eleven crossed plants now averaged 68.1, and the eleven
self-fertilised plants 62.34 inches in height; or as 100 to 91. In all
four pots a crossed plant flowered before any one of the
self-fertilised; but three of the plants did not flower at all. Those
that flowered were also measured to the summits of the male flowers: the
ten crossed plants averaged 66.51, and the nine self-fertilised plants
61.59 inches in height; or as 100 to 93.
A large number of the same crossed and self-fertilised seeds were sown
in the middle of the summer in the open ground in two long rows. Very
much fewer of the self-fertilised than of the crossed plants produced
flowers; but those that did flower, flowered almost simultaneously. When
fully grown the ten tallest plants in each row were selected and
measured to the tips of their highest leaves, as well as to the summits
of their male flowers. The crossed averaged to the tips of their leaves
54 inches in height, and the self-fertilised 44.65, or as 100 to 83; and
to the summits of their male flowers, 53.96 and 43.45 inches; or as 100
to 80.
Phalaris canariensis.
Hildebrand has shown in the paper referred to under the last species,
that this hermaphrodite grass is better adapted for cross-fertilisation
than for self-fertilisation. Several plants were raised in the
greenhouse close together, and their flowers were mutually intercrossed.
Pollen from a single plant growing quite separately was collected and
placed on the stigmas of the same plant. The seeds thus produced were
self-fertilised, for they were fertilised with pollen from the same
plant, but it will have been a mere chance whether with pollen from the
same flowers. Both lots of seeds, after germinating on sand, were
planted in pairs on the opposite sides of four pots, which were kept in
the greenhouse. When the plants were a little over a foot in height they
were measured, and the crossed plants averaged 13.38, and the
self-fertilised 12.29 inches in height; or as 100 to 92.
When in full flower they were again measured to the extremities of their
culms, as shown in Table 6/98.
TABLE 6/98. Phalaris canariensis.
Heights of plants measured in inches.
Column 1: Number (Name) of Pot.
Column 2: Crossed Plants.
Column 3: Self-fertilised Plants.
Pot 1 : 42 2/8 : 41 2/8.
Pot 1 : 39 6/8 : 45 4/8.
Pot 2 : 37 : 31 6/8.
Pot 2 : 49 4/8 : 37 2/8.
Pot 4 : 29 : 42 3/8.
Pot 2 : 37 : 34 7/8.
Pot 3 : 37 6/8 : 28.
Pot 3 : 35 4/8 : 28.
Pot 3 : 43 : 34.
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