individuals of the same species, see H. Muller 'Die Befruchtung' etc. pages 285,
339.) On cultivated trees of the Walnut and Mulberry, the male flowers have been
observed to abort on certain individuals, which have thus been converted into
females; but whether there are any species in a state of nature which co-exist
as monoecious and female individuals, I do not know. (Introduction/18.
'Gardener's Chronicle' 1847 pages 541, 558.)

The third Class consists of dioecious species, and the remarks made under the
last class with respect to the amount of difference between the male and female
flowers are here applicable. It is at present an inexplicable fact that with
some dioecious plants, of which the Restiaceae of Australia and the Cape of Good
Hope offer the most striking instance, the differentiation of the sexes has
affected the whole plant to such an extent (as I hear from Mr. Thiselton Dyer)
that Mr. Bentham and Professor Oliver have often found it impossible to match
the male and female specimens of the same species. In my seventh chapter some
observations will be given on the gradual conversion of heterostyled and of
ordinary hermaphrodite plants into dioecious or sub-dioecious species.

The fourth and last Class consists of the plants which were called polygamous by
Linnaeus; but it appears to me that it would be convenient to confine this term
to the species which coexist as hermaphrodites, males and females; and to give
new names to several other combinations of the sexes--a plan which I shall here
follow. Polygamous plants, in this confined sense of the term, may be divided
into two sub-groups, according as the three sexual forms are found on the same
individual or on distinct individuals. Of this latter or trioicous sub-group,
the common Ash (Fraxinus excelsior) offers a good instance: thus, I examined
during the spring and autumn fifteen trees growing in the same field; and of
these, eight produced male flowers alone, and in the autumn not a single seed;
four produced only female flowers, which set an abundance of seeds; three were
hermaphrodites, which had a different aspect from the other trees whilst in