Family Melianthaceae

Melianthaceae Link

Excluding Francoaceae

Habit and leaf form. Rather small trees, or shrubs (or half-shrubs). Leaves alternate; compound; pinnate. Lamina pinnately veined. Leaves stipulate. Stipules intrapetiolar (connate, often large).

Leaf anatomy. Stomata present; anomocytic.

Lamina dorsiventral. The mesophyll containing calcium oxalate crystals. The mesophyll crystals solitary-prismatic (styloids). Minor leaf veins without phloem transfer cells (Bersama).

Stem anatomy. Cork cambium present; initially deep-seated. Nodes multilacunar. Medullary bundles present. Internal phloem absent. Secondary thickening anomalous. ‘Included’ phloem absent. Xylem without fibre tracheids; with libriform fibres (short or very short); with vessels. Vessel end-walls simple. Primary medullary rays wide. Wood storied; parenchyma paratracheal.

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 unit 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, biochemistry. Not cyanogenic. Iridoids not detected. Proanthocyanidins absent. Flavonols present; quercetin. Ellagic acid present (2 genera). Saponins/sapogenins absent. Aluminium accumulation not found. Sugars transported as sucrose (Melianthus).

Geography, cytology. Paleotropical and Cape. Sub-tropical to tropical. Tropical and southern Africa. N = 18 or 19.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rosiflorae; Rosales (?). Cronquist’s Subclass Rosidae; Sapindales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Geraniales.

Species 15. Genera 2; Bersama, Melianthus.

Illustrations.
• Technical details: Bersama, Melianthus.
• Technical details: Bersama (Thonner).