scoparia, an inhabitant of Tasmania, I did not doubt that it
was heterostyled; but on examining some flowers sent me by Dr. Hooker they
proved to be dioecious. The male flowers have large anthers and a very small
ovarium, surmounted by a mere vestige of a stigma without any style; whilst the
female flowers possess a large ovarium, the anthers being rudimentary and
apparently quite destitute of pollen. Considering how many Rubiaceous genera are
heterostyled, it is a reasonable suspicion that this Asperula is descended from
a heterostyled progenitor; but we should be cautious on this head, for there is
no improbability in a homostyled Rubiaceous plant becoming dioecious. Moreover,
in an allied plant, Galium cruciatum, the female organs have been suppressed in
most of the lower flowers, whilst the upper ones remain hermaphrodite; and here
we have a modification of the sexual organs without any connection with
heterostylism.
Mr. Thwaites informs me that in Ceylon various Rubiaceous plants are
heterostyled; but in the case of Discospermum one of the two forms is always
barren, the ovary containing about two aborted ovules in each loculus; whilst in
the other form each loculus contains several perfect ovules; so that the species
appears to be strictly dioecious.
Most of the species of the South American genus Aegiphila, a member of the
Verbenaceae, apparently are heterostyled; and both Fritz Muller and myself
thought that this was the case with Ae.
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