The Different Forms of Flowers on Plants of the Same Species   By: Charles Darwin (1809-1882)

THE DIFFERENT FORMS OF FLOWERS ON PLANTS OF THE SAME SPECIES

by CHARLES DARWIN, M.A., F.R.S.

TO

PROFESSOR ASA GRAY

THIS VOLUME IS DEDICATED BY THE AUTHOR AS A SMALL TRIBUTE OF RESPECT AND AFFECTION.

CONTENTS.

INTRODUCTION.

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.