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
14 flowers fertilised by the shortest stamens of the mid-styled.
3 0
0 0
0 0
0 0
0 0
- 0
0 0
0
Too sterile for any average.
TABLE 4.23.4. Illegitimate union.
12 flowers fertilised by the mid-length stamens of the short-styled.
20 0
0 0
0 0
0 0
- 0
0 0
0
Too sterile for any average.
TABLE 4.23.5. Illegitimate union.
15 flowers fertilised by own-form mid-length stamens.
2 -
10 0
23 0
0 0
0 0
0 0
0 0
0 0
Too sterile for any average.
TABLE 4.23.6. Illegitimate union.
15 flowers fertilised by own-form shortest stamens.
4 -
8 0
4 0
0 0
0 0
0 0
0 0
0 0
Too sterile for any average.
Besides the above experiments, I fertilised a considerable number of long-styled
flowers with pollen, taken by a camel’s-hair brush, from both the mid-length and
shortest stamens of their own form: only 5 capsules were produced, and these
yielded on an average 14.5 seeds. In 1863 I tried a much better experiment: a
long-styled plant was grown by itself, miles away from any other plant, so that
the flowers could have received only their own two kinds of pollen. The flowers
were incessantly visited by bees, and their stigmas must have received
successive applications of pollen on the most favourable days and at the most
favourable hours: all who have crossed plants know that this highly favours
fertilisation. This plant produced an abundant crop of capsules; I took by
chance 20 capsules, and these contained seeds in number as follows:--
20 20 35 21 19
26 24 12 23 10
7 30 27 29 13
20 12 29 19 35
This gives an average of 21.5 seeds per capsule. As we know that the long-styled
form, when standing near plants of the other two forms and fertilised by
insects, produces on an average 93 seeds per capsule, we see that this form,
fertilised by its own two pollens, yields only between one-fourth and one-fifth
of the full number of seed. I have spoken as if the plant had received both its
own kinds of pollen, and this is, of course, possible; but, from the enclosed
position of the shortest stamens, it is much more probable that the stigma
received exclusively pollen from the mid-length stamens; and this, as may be
seen in Table 4.23.5, is the more fertile of the two self-unions.
TABLE 4.24. Lythrum salicaria, mid-styled form.
TABLE 4.24.1. Legitimate union.
12 flowers fertilised by the mid-length stamens of the long-styled. These
stamens equal in length the pistil of the mid-styled.
Product of good seed in each capsule.
138 122
149 50
147 151
109 119
133 138
144 0
-
92 percent of these flowers (probably 100 per cent) yielded capsules. Each
capsule contained, on an average, 127.3 seeds.
TABLE 4.24.2. Legitimate union.
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