Nauclea L.

Scientific Description

Family Rubiaceae.

Habit and leaf form. Trees. Young stems cylindrical. Helophytic, or mesophytic, or xerophytic. Leaves opposite; petiolate; connate (via the stipules), or not connate; gland-dotted, or not gland-dotted; simple; epulvinate. Leaf blades entire; pinnately veined; cross-venulate. Leaves with stipules. Stipules interpetiolar (free); with colleters (secreting mucilage), or without colleters; the terminal pair persistent (lower pairs often caducous). Leaf blade margins entire, or serrate. Leaves without a persistent basal meristem. Domatia recorded (sometimes present on lower surface), or not recorded (then absent). Stem anatomy. Nodes unilacunar, or tri-lacunar. Secondary thickening developing from a conventional cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Plants homostylous, or heterostylous. Entomophilous. Pollination mechanism conspicuously specialized (with passive pollen presentation involving stylar modification), or unspecialized.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in heads (heads pedunculate). The terminal inflorescence unit cymose. Inflorescences terminal, or terminal and axillary. Flowers small to medium-sized; regular; 4 merous, or 5 merous; cyclic; tetracyclic. Free hypanthium present, or absent (depending on interpretation). Perianth with distinct calyx and corolla; 8, or 10; 2 -whorled; the two whorls isomerous. Calyx 4, or 5; 1 -whorled; gamosepalous; lobed; glabrous, or hairy (inside); open in bud; regular. Calyx lobes triangular, oblong or spathulate. Corolla 4, or 5; 1 -whorled; gamopetalous; imbricate; tubular to funnel-shaped; regular; yellow (in N. orientalis). Androecium 4, or 5. Androecial members adnate (to the corolla tube); free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 4, or 5. Staminal insertion in the throat of the corolla tube. Stamens becoming exserted; isomerous with the perianth; oppositisepalous; filantherous (filaments very short). Anthers basifixed; dehiscing via longitudinal slits; introrse; tetrasporangiate. Pollen shed in aggregates, or shed as single grains; if aggregated, in tetrads. Gynoecium 2 carpelled. The pistil 2 celled. Carpels reduced in number relative to the perianth. Gynoecium syncarpous; eu-syncarpous; inferior. Ovary plurilocular; 2 locular. Gynoecium transverse. Epigynous disk present. Gynoecium stylate. Styles 1; simple (filiform); attenuate from the ovary, or from a depression at the top of the ovary; apical; shorter than the ovary at anthesis to much longer than the ovary at anthesis; becoming exserted. Stigmas 1; 1 - lobed; capitate or spindle-shaped; wet type, or dry type; papillate, or non-papillate; Group II type and Group IV type. Placentation axile. Ovules 10–50 per locule (i.e ‘numerous’); mostly pendulous, or horizontal to ascending (but these mostly aborting); anatropous, or hemianatropous.

Fruit and seed features. Fruit fleshy (succulent); indehiscent. Gynoecia of adjoining flowers combining to form a multiple fruit (flowers connate by their ovaries). Fruit 10–100 seeded (i.e. ‘numerous’). Seeds ovoid or ellipsoid; endospermic, or non-endospermic. Endosperm ruminate, or not ruminate; when present, oily. Cotyledons 2. Embryo straight, or curved. Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, biochemistry. Aluminium accumulation demonstrated, or not found.

Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia and Northern Territory.

Etymology. From the Greek for "ship" and "to confine"; the half capsule is boat-shaped.