| → can most effectually 1859 1860 1861 |
| can effectually 1866 |
| OMIT 1869 1872 |
|
| → one— not as a very striking case, but 1859 1860 1861 1866 |
| one, 1869 1872 |
|
| → pollen grains, 1861 |
| pollen-grains, 1859 1860 1866 |
| a few pollen-grains, 1869 |
| a few pollen grains, 1872 |
|
| → accidentally dusted with pollen, having 1859 1860 1861 1866 |
| which had 1869 1872 |
|
|
regularly carry pollen from flower to flower; and that they
→can most effectually
do
could easily show by many striking
I will give only
→one— not as a very striking case, but
as likewise illustrating one step in the separation of the sexes of
Some holly-trees bear only male flowers, which have four stamens producing
small quantity of pollen, and a rudimentary pistil; other
bear only female flowers; these have a full-sized pistil, and four stamens with shrivelled anthers, in which not a grain of pollen can be detected. Having found a female tree exactly sixty yards from a male tree, I put the stigmas of twenty flowers, taken from different branches, under the microscope, and on all, without exception, there were
→pollen grains,
and on some a
As the wind had set for several days from the female to the male tree, the pollen could not thus have been carried. The weather had been cold and boisterous, and therefore not favourable to bees, nevertheless every female flower which I examined had been effectually fertilised by the bees,
→accidentally dusted with pollen, having
flown from tree to tree in search of nectar. But to return to our imaginary case: as soon as the plant had been rendered so highly attractive to insects that pollen was regularly carried from flower to flower, another process might commence. No naturalist doubts the advantage of what has been called the "physiological division of labour;" hence we may believe that it would be advantageous to a plant to produce stamens alone in one flower or on one whole plant, and pistils alone in another flower or on another plant. In plants under culture and placed under new conditions of life, sometimes the male organs and sometimes the female organs become more or less impotent; now if we suppose this to
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