Prev | Current Page 117 | Next

Darwin, Charles, 1809-1882

"The Different Forms of Flowers on Plants of the Same Species"

Seed sown
later in the flower-garden yielded seventeen long-styled and twelve short-styled
forms. These facts justify the statement that the two forms are produced in
about equal numbers. The thirty-four plants of the first lot were kept under a
net which excluded all insects, except such minute ones as Thrips. I fertilised
fourteen long-styled flowers legitimately with pollen from the short-styled, and
got eleven fine seed-capsules, which contained on an average 8.6 seeds per
capsule, but only 5.6 appeared to be good. It may be well to state that ten
seeds is the maximum production for a capsule, and that our climate cannot be
very favourable to this North-African plant. On three occasions the stigmas of
nearly a hundred flowers were fertilised illegitimately with their own-form
pollen, taken from separate plants, so as to prevent any possible ill effects
from close inter-breeding. Many other flowers were also produced, which, as
before stated, must have received plenty of their own pollen; yet from all these
flowers, borne by the seventeen long-styled plants, only three capsules were
produced. One of these included no seed, and the other two together gave only
five good seeds. It is probable that this miserable product of two half-fertile
capsules from the seventeen plants, each of which must have produced at least
fifty or sixty flowers, resulted from their fertilisation with pollen from the
short-styled plants by the aid of Thrips; for I made a great mistake in keeping
the two forms under the same net, with their branches often interlocking; and it
is surprising that a greater number of flowers were not accidentally fertilised.


Pages:
105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129