Hooker calculates that out of about 756
phanerogamic plants inhabiting the islands, no less than 108 are trees,
belonging to thirty-five families. Of these 108 trees, fifty-two, or
very nearly half, have their sexes more or less separated. Of bushes
there are 149, of which sixty-one have their sexes in the same state;
whilst of the remaining 500 herbaceous plants only 121, or less than a
fourth, have their sexes separated. Lastly, Professor Asa Gray informs
me that in the United States there are 132 native trees (belonging to
twenty-five families) of which ninety-five (belonging to seventeen
families) "have their sexes more or less separated, for the greater part
decidedly separated.") It is, however, doubtful how far this rule holds
good generally, and it certainly does not do so in Australia. But I have
been assured that the flowers of the prevailing Australian trees,
namely, the Myrtaceae, swarm with insects, and if they are dichogamous
they would be practically diclinous. (10/61. With respect to the
Proteaceae of Australia, Mr. Bentham 'Journal of the Linnean Society
Botany' volume 13 1871 pages 58, 64, remarks on the various contrivances
by which the stigma in the several genera is screened from the action of
the pollen from the same flower. For instance, in Synaphea "the stigma
is held by the eunuch (i.e., one of the stamens which is barren) safe
from all pollution from her brother anthers, and is preserved intact for
any pollen that may be inserted by insects and other agencies.
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