| ↑ 1 blocks not present in 1859 1860 1861; present in 1866 1869 1872 |
| It would take up too much space to show the various steps, through dimorphism and other means, by which the separation of the sexes in plants of various kinds is apparently now in progress; but I may add that some of the species of holly in North America
are, according to Asa Gray, in an intermediate
condition, or, as he expresses himself, the flowers
are more or less diœciously polygamous.
|
|
| → in our imaginary case: 1859 1860 1861 1866 |
| OMIT 1869 1872 |
|
| → they can, with a very little more trouble, 1859 1860 1861 1866 1869 |
| with a very little more trouble, they can 1872 |
|
| → I can see no reason to doubt that an accidental deviation 1859 1860 1861 |
| it may be believed that an accidental deviation 1866 |
| it may be believed that under certain circumstances individual differences 1869 1872 |
|
| → size and form 1859 1860 1861 1866 |
| curvature or length 1869 1872 |
|
| → body, or in the curvature and length of the 1859 1860 1861 1866 |
| OMIT 1869 1872 |
|
| → and so have a better chance of living and leaving descendants. 1859 1860 1861 1866 |
| than others; and thus the communities to which they belonged would flourish and throw off many swarms inheriting the same peculiarities. 1869 1872 |
|
| → offer in vain 1859 1860 1861 1866 1872 |
| in vain offer 1869 |
|
|
occur in ever so slight a degree under nature,
as pollen is already carried regularly from flower to flower, and as a more complete separation of the sexes of our plant would be advantageous on the principle of the division of labour, individuals with this tendency more and more increased, would be continually favoured or selected, until at last a complete separation of the sexes
be effected. ↑
|
|
| Let us now turn to the nectar-feeding
→in our imaginary case:
we may suppose the
of which we have been slowly increasing the nectar by continued selection, to be a common plant; and that certain insects depended in main part on its nectar for food. I could give many
showing how anxious bees are to save
for instance, their habit of cutting holes and sucking the nectar at the bases of certain flowers, which
→they can, with a very little more trouble,
enter by the mouth. Bearing such facts in mind,
→I can see no reason to doubt that an accidental deviation
in the
→size and form
of the
→body, or in the curvature and length of the
proboscis, &c.,
too slight to be appreciated by us, might profit a bee or other insect, so that
would be able to obtain
food more
→and so have a better chance of living and leaving descendants. Its descendants would probably inherit a tendency to a similar slight deviation of structure. The tubes of the
of the common red and incarnate clovers (Trifolium pratense and incarnatum) do not on a hasty glance appear to differ in length; yet the hive-bee can easily suck the nectar out of the incarnate clover, but not out of the common red clover, which is visited by humble-bees alone; so that whole fields of the red clover
→offer in vain
an abundant supply of precious nectar to the hive-bee.
The
|
