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.
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.
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.
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.
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.