The families of flowering plants
Habit and leaf form. Rather small trees, or shrubs (or half-shrubs). Leaves alternate; compound; pinnate; imparipinnate. Lamina pinnately veined. Leaves stipulate. Stipules intrapetiolar (connate, often large).
Leaf anatomy. The leaf lamina dorsiventral. Mucilaginous epidermis absent. Stomata present; mainly confined to one surface (abaxial); anomocytic. Hairs present (at least sometimes), or absent (?). Complex hairs stellate (in Melianthus), or peltate. The mesophyll containing crystals. The crystals solitary-prismatic (notably styloids, often on the boundary between palisade and mesophyll). Minor leaf veins without phloem transfer cells (Bersama).
Axial (stem, wood) anatomy. Secretory cavities absent. Cork cambium present; initially deep-seated. Nodes multilacunar. Primary vascular tissues comprising a ring of bundles (at first, these widely separated), or comprising a ring of bundles (later); collateral. Internal phloem absent. Cortical bundles absent. Medullary bundles present (these concentric, each consisting of a central strand of phloem surrounded by a ring of fibres, rarely with a few isolated vessels: see illustration). Secondary thickening developing from a conventional cambial ring. Primary medullary rays wide.
The wood diffuse porous. The vessels moderately small; solitary, radially paired, and in radial multiples. The vessel end-walls simple. The vessels with spiral thickening, or without spiral thickening. The axial xylem without fibre tracheids; with libriform fibres (these short or very short); including septate fibres (rarely), or without septate fibres. The fibres without spiral thickening. The parenchyma paratracheal. The secondary phloem not stratified. Included phloem absent. The wood storied to partially storied. Tyloses absent.
Reproductive type, pollination. Plants hermaphrodite (usually), or polygamodioecious. Floral nectaries present. Nectar secretion from the disk.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in inflorescences; in racemes. The ultimate inflorescence units racemose. Inflorescences racemes. Flowers medium-sized to large; very irregular; zygomorphic; resupinate (by twisting of the pedicels). The floral irregularity involving the perianth, or involving the perianth and involving the androecium. Flowers cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk present; extrastaminal; of separate members, or annular (unilateral).
Perianth with distinct calyx and corolla; 8–10; 2 whorled; isomerous, or anisomerous. Calyx 5, or 4 (by union of two members); 1 whorled; polysepalous, or partially gamosepalous, or gamosepalous; unequal but not bilabiate, or bilabiate; basally appendaged to spurred (one sepal spurred or saccate-gibbous in Melianthus), or neither appendaged nor spurred; imbricate. Corolla 4 (by one being abortive), or 5; 1 whorled; polypetalous; imbricate; unequal but not bilabiate (or one member aborted). Petals clawed.
Androecium 4, or 5. Androecial members free of the perianth; all equal to markedly unequal; free of one another, or coherent (the filaments sometimes basally united); 1 whorled. Androecium exclusively of fertile stamens. Stamens 4, or 5 (often declinate); isomerous with the perianth; oppositisepalous. Anthers dorsifixed; slightly versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate. Endothecium not developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral. Anther wall initially with more than one middle layer (3). Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate; 3-celled (in both genera).
Gynoecium 4(–5) carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil 4(–5) celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 4(–5) locular. Gynoecium stylate. Styles 1; from a depression at the top of the ovary; apical. Stigmas 1; truncate or apically dentate. Placentation basal to axile, or axile to apical. Ovules 1 per locule (Bersama), or 2–5 per locule (Melianthus); pendulous to horizontal, or ascending; apotropous; with ventral raphe, or with dorsal raphe (according to whether erect or pendulous); arillate (Bersama), or non-arillate; anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle, or not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids hooked. Endosperm formation nuclear.
Fruit non-fleshy; dehiscent; a capsule (papery or woody, often longitudinally grooved, sometimes apically lobed). Capsules loculicidal (or opening only at the tip). Seeds copiously endospermic. Endosperm oily (and sometimes starchy). Seeds with starch, or without starch. Seeds with amyloid. Embryo well differentiated (small). Cotyledons 2. Embryo chlorophyllous; straight.
Seedling. Germination phanerocotylar.
Physiology, phytochemistry. Sugars transported as sucrose (Melianthus). Not cyanogenic. Iridoids not detected. Saponins/sapogenins absent. Proanthocyanidins absent. Flavonols present; quercetin. Ellagic acid present (2 genera). Aluminium accumulation not found.
Geography, cytology. Paleotropical and Cape. Sub-tropical to tropical. Tropical and southern Africa. N = 18 or 19.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgrens Superorder Rosiflorae; Rosales (?). Cronquists Subclass Rosidae; Sapindales. APG III core angiosperms; core eudicot; Superorder Rosanae; malvid. APG IV Order Geraniales.
Species 15. Genera 2; Bersama, Melianthus.
General remarks. Francoaceae are rightly excluded for practical purposes, with reference to differences in numerous, conspicuous morphological characters.
Economic uses, etc. Some species of Melianthus (e.g., M. comosus and M. major) are reputed to be toxic to livestock, and have also been associated with poisonous honey.
Illustrations. • Le Maout and Decaisne: Bersama, Melianthus. • Bersama abyssinica: Thonner. • Bersama tysoniana: Hook. Ic. Pl. 23 (1894). • Melianthus major: Bot. Reg. 1 (1815). • Melianthus major: TS pith, with concentric medullary bundles (Solereder, 1908).
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: 15th April 2018. delta-intkey.com/angio’.