The families of flowering plants
Habit and leaf form. Erect, branched herbs. Plants non-succulent. Annual, or biennial (sometimes glandular); without conspicuous aggregations of leaves. Leaves opposite; not gland-dotted; simple. Lamina entire; linear to lanceolate, or ovate; attenuate at the base. Leaves exstipulate. Lamina margins entire.
Leaf anatomy. The leaf lamina bifacial, or centric.
Axial (stem, wood) anatomy. Cork cambium present; initially superficial (in the epidermis). Internal phloem absent. Cortical bundles absent. Medullary bundles absent.
Reproductive type, pollination. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in inflorescences; in cymes. The ultimate inflorescence units cymose. Inflorescences terminal and axillary; sympodial, cymose, the flowers paired. Flowers regular; 5 merous; cyclic; tetracyclic. Free hypanthium absent.
Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous; regular; valvate. Corolla 5; 1 whorled; polypetalous (the petals shorter than the sepals); imbricate; regular; white, or yellow. Petals ovate-spathulate.
Androecium 5. Androecial members free of the perianth (inserted on the margin of the epigynous disk); all equal; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 5; isomerous with the perianth; oppositisepalous; alternating with the corolla members; filantherous (the filaments subulate). Anthers dorsifixed; dehiscing via longitudinal slits; introrse; tetrasporangiate. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral. Tapetum glandular (?, the cells becoming binucleate). Pollen grains 2-celled.
Gynoecium 2–3 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled. Gynoecium syncarpous; synovarious; inferior. Ovary 1 locular. Epigynous disk present (inconspicuous). Gynoecium stylate. Styles 2–3 (thick, divaricate); free; apical. Stigmas 2–3; dorsal to the carpels (according to Hutchinson); capitate. Placentation apical (with 23 remarkably large, pendulous, apical placentas). Ovules in the single cavity 50–200 (very numerous); pendulous; anatropous; bitegmic; tenuinucellate. Outer integument not contributing to the micropyle. Endothelium differentiated. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; persistent. Synergids hooked. Endosperm formation cellular. Endosperm haustoria present; chalazal. Embryogeny caryophyllad.
Fruit non-fleshy; dehiscent; a capsule. Capsules apically 23 valvular. Fruit 50–200 seeded (very numerous). Seeds minute; appendaged.
Physiology, phytochemistry. Iridoids detected (S.R. Jensen, unpublished); Route I type.
Geography, cytology. Paleotropical and Cape. Temperate to tropical. Tropical and South Africa to Northwest India.
Taxonomy. Subclass Dicotyledonae; Tenuinucelli (polypetalous, but iridoids present and ovules tenuinucellate). Dahlgrens Superorder Rosiflorae; Saxifragales. Cronquists Subclass Rosidae; Rosales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; lamiid; Order unassigned.
Species 5. Genera 1; only genus, Bistella (Vahlia).
Illustrations. • Vahlia dichotoma: Hutchinson. • Vahlia oldenlandioides: R. Wight 2 (1850).
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 24th October 2017. delta-intkey.com/angio’.