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Darwin, Charles, 1809-1882

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

The two heaps were of very nearly equal
bulk; but the heads from the female plant numbered 160, and their seeds weighed
8.7 grains; whilst those from the hermaphrodite plant numbered 200, and their
seeds weighed only 4.9 grains; so that the seeds from the female plant were to
those from the hermaphrodite as 100 to 56 in weight. If the relative weight of
the seeds from an equal number of flower-heads from the two forms be compared,
the ratio is as 100 for the female to 45 for the hermaphrodite form.
Thymus vulgaris.
(FIGURE 7.15. Thymus vulgaris (magnified).
Left: Hermaphrodite.
Right: Two females.)
The common garden thyme resembles in almost every respect T. serpyllum. The same
slight differences between the stigmas of the two forms could be perceived. In
the females the stamens are not generally quite so much reduced as in the same
form of T. serpyllum. In some specimens sent me from Mentone by Mr. Moggridge,
together with the sketches in Figure 7.15, the anthers of the female, though
small, were well formed, but they contained very little pollen, and not a single
sound grain could be detected. Eighteen seedlings were raised from purchased
seed, sown in the same small bed; and these consisted of seven hermaphrodites
and eleven females. They were left freely exposed to the visits of bees, and no
doubt every female flower was fertilised; for on placing under the microscope a
large number of stigmas from female plants, not one could be found to which
pollen-grains of thyme did not adhere.


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