CONCLUDING REMARKS ON HETEROSTYLED PLANTS.

The essential character of heterostyled plants.--Summary of the differences in
fertility between legitimately and illegitimately fertilised plants.--Diameter
of the pollen-grains, size of anthers and structure of stigma in the different
forms.--Affinities of the genera which include heterostyled species.--Nature of
the advantages derived from heterostylism.--The means by which plants became
heterostyled.--Transmission of form.--Equal-styled varieties of heterostyled
plants.--Final remarks.


CHAPTER VII.
POLYGAMOUS, DIOECIOUS, AND GYNO-DIOECIOUS PLANTS.

The conversion in various ways of hermaphrodite into dioecious plants.--
Heterostyled plants rendered dioecious.--Rubiaceae.--Verbenaceae.--Polygamous
and sub-dioecious plants.--Euonymus.--Fragaria.--The two sub-forms of both sexes
of Rhamnus and Epigaea.--Ilex.--Gyno-dioecious plants.--Thymus, difference in
fertility of the hermaphrodite and female individuals.--Satureia.--Manner in
which the two forms probably originated.--Scabiosa and other gyno-dioecious
plants.--Difference in the size of the corolla in the forms of polygamous,
dioecious, and gyno-dioecious plants.


CHAPTER VIII.
CLEISTOGAMIC FLOWERS.

General character of cleistogamic flowers.--List of the genera producing such
flowers, and their distribution in the vegetable series.--Viola, description of
the cleistogamic flowers in the several species; their fertility compared with