It is, however, possible
that the flowers may be in the same state as those of the common thyme and of
several other Labiatae, in which females and hermaphrodites regularly co-exist.
Fritz Muller, who thought that the present plant was heterostyled, as I did at
first, informs me that he found bushes in several places growing quite isolated,
and that these were completely sterile; whilst two plants growing close together
were covered with fruit. This fact agrees better with the belief that the
species is dioecious than that it consists of hermaphrodites and females; for if
any one of the isolated plants had been an hermaphrodite, it would probably have
produced some fruit.]
RUBIACEAE.
This great natural family contains a much larger number of heterostyled genera
than any other one, as yet known.
Mitchella repens.
Professor Asa Gray sent me several living plants collected when out of flower,
and nearly half of these proved long-styled, and the other half short-styled.
The white flowers, which are fragrant and which secrete plenty of nectar, always
grow in pairs with their ovaries united, so that the two together produce "a
berry-like double drupe." (3/22. A. Gray 'Manual of the Botany of the United
States' 1856 page 172.) In my first series of experiments (1864) I did not
suppose that this curious arrangement of the flowers would have any influence on
their fertility; and in several instances only one of the two flowers in a pair
was fertilised; and a large proportion or all of these failed to produce
berries.
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