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
So that a cross with pollen from a fresh stock greatly increased the
productiveness of the flowers on plants which had been self-fertilised
for the four previous generations, in comparison not only with the
flowers on the same plants self-fertilised for the fifth time, but with
the flowers on the crossed plants crossed with pollen from another plant
of the same old stock for the fifth time.
These three lots of seeds were placed on sand, and were planted in an
equal state of germination in seven pots, each made tripartite by three
superficial partitions. Some of the remaining seeds, whether or not in a
state of germination, were thickly sown in an eighth pot. The pots were
kept in the greenhouse, and the plants trained up sticks. They were
first measured to the tops of their stems when coming into flower; and
the twenty-two Westerham-crossed plants then averaged 25.51 inches; the
twenty-three intercrossed plants 30.38; and the twenty-three
self-fertilised plants 23.40 inches in height. We thus get the following
ratios:--
The Westerham-crossed plants in height to the self-fertilised as 100 to
91.
The Westerham-crossed plants in height to the intercrossed as 100 to
119.
The intercrossed plants in height to the self-fertilised as 100 to 77.
These plants were again measured when their growth appeared on a casual
inspection to be complete. But in this I was mistaken, for after cutting
them down, I found that the summits of the stems of the
Westerham-crossed plants were still growing vigorously; whilst the
intercrossed had almost, and the self-fertilised had quite completed
their growth. Therefore I do not doubt, if the three lots had been left
to grow for another month, that the ratios would have been somewhat
different from those deduced from the measurements in Table 6/82.
TABLE 6/82. Petunia violacea.
Heights of plants measured in inches.
Column 1: Number (Name) of Pot.
Column 2: Westerham-Crossed Plants (from self-fertilised Plants of
fourth generation crossed by a fresh stock).
Column 3: Intercrossed Plants (Plants of one and the same stock
intercrossed for five generations).
Column 4: Self-fertilised Plants (self-fertilised for five generations).
Pot 1 : 64 5/8 : 57 2/8 : 43 6/8.
Pot 1 : 24 : 64 : 56 3/8.
Pot 1 : 51 4/8 : 58 6/8 : 31 5/8.
Pot 2 : 48 7/8 : 59 7/8 : 41 5/8.
Pot 2 : 54 4/8 : 58 2/8 : 41 2/8.
Pot 2 : 58 1/8 : 53 : 18 2/8.
Pot 3 : 62 : 52 2/8 : 46 6/8.
Pot 3 : 53 2/8 : 54 6/8 : 45.
Pot 3 : 62 7/8 : 61 6/8 : 19 4/8.
Pot 4 : 44 4/8 : 58 7/8 : 37 5/8.
Pot 4 : 49 2/8 : 65 2/8 : 33 2/8.
Pot 4 : .. : 59 6/8 : 32 2/8.
Pot 5 : 43 1/8 : 35 6/8 : 41 6/8.
Pot 5 : 53 7/8 : 34 6/8 : 26 4/8.
Pot 5 : 53 2/8 : 54 6/8 : 0.
Pot 6 : 37 4/8 : 56 : 46 4/8.
Pot 6 : 61 : 63 5/8 : 29 6/8.
Pot 6 : 0 : 57 7/8 : 14 4/8.
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