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Overview
CHAPTER I.
HETEROSTYLED DIMORPHIC PLANTS: PRIMULACEAE.
Primula veris or the cowslip.--Differences in structure between the two forms.--
Their degrees of fertility when legitimately and illegitimately united.--P.
elatior, vulgaris, Sinensis, auricula, etc.--Summary on the fertility of the
heterostyled species of Primula.--Homostyled species of Primula.--Hottonia
palustris.--Androsace vitalliana.
CHAPTER II.
HYBRID PRIMULAS.
The oxlip a hybrid naturally produced between Primula veris and vulgaris.--The
differences in structure and function between the two parent-species.--Effects
of crossing long-styled and short-styled oxlips with one another and with the
two forms of both parent-species.--Character of the offspring from oxlips
artificially self-fertilised and cross-fertilised in a state of nature.--Primula
elatior shown to be a distinct species.--Hybrids between other heterostyled
species of Primula.--Supplementary note on spontaneously produced hybrids in the
genus Verbascum.
CHAPTER III.
HETEROSTYLED DIMORPHIC PLANTS--continued.
Linum grandiflorum, long-styled form utterly sterile with own-form pollen.--
Linum perenne, torsion of the pistils in the long-styled form alone.--Homostyled
species of Linum.--Pulmonaria officinalis, singular difference in self-fertility
between the English and German long-styled plants.--Pulmonaria angustifolia
shown to be a distinct species, long-styled form completely self-sterile.--
Polygonum fagopyrum.--Various other heterostyled genera.--Rubiaceae.--Mitchella
repens, fertility of the flowers in pairs.--Houstonia.--Faramea, remarkable
difference in the pollen-grains of the two forms; torsion of the stamens in the
short-styled form alone; development not as yet perfect.--The heterostyled
structure in the several Rubiaceous genera not due to descent in common.
CHAPTER IV.
HETEROSTYLED TRIMORPHIC PLANTS.
Lythrum salicaria.--Description of the three forms.--Their power and complex
manner of fertilising one another.--Eighteen different unions possible.--Mid-
styled form eminently feminine in nature.--Lythrum Graefferi likewise
trimorphic.--L. hymifolia dimorphic.--L. hyssopifolia homostyled.--Nesaea
verticillata trimorphic.--Lagerstroemia, nature doubtful.--Oxalis, trimorphic
species of.--O. Valdiviana.--O. Regnelli, the illegitimate unions quite barren.-
-O. speciosa.--O. sensitiva.--Homostyled species of Oxalis.--Pontederia, the one
monocotyledonous genus known to include heterostyled species.
CHAPTER V.
ILLEGITIMATE OFFSPRING OF HETEROSTYLED PLANTS.
Illegitimate offspring from all three forms of Lythrum salicaria.--Their dwarfed
stature and sterility, some utterly barren, some fertile.--Oxalis, transmission
of form to the legitimate and illegitimate seedlings.--Primula Sinensis,
illegitimate offspring in some degree dwarfed and infertile.--Equal-styled
varieties of P. Sinensis, auricula, farinosa, and elatior.--P. vulgaris, red-
flowered variety, illegitimate seedlings sterile.--P. veris, illegitimate plants
raised during several successive generations, their dwarfed stature and
sterility.--Equal-styled varieties of P. veris.--Transmission of form by
Pulmonaria and Polygonum.--Concluding remarks.--Close parallelism between
illegitimate fertilisation and hybridism.
CHAPTER VI.
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
that of the perfect flowers.--Oxalis acetosella.--O. sensitiva, three forms of
cleistogamic flowers.--Vandellia.--Ononis.--Impatiens.--Drosera.--Miscellaneous
observations on various other cleistogamic plants.--Anemophilous species
producing cleistogamic flowers.--Leersia, perfect flowers rarely developed.--
Summary and concluding remarks on the origin of cleistogamic flowers.--The chief
conclusions which may be drawn from the observations in this volume.
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