Including Stilbeaceae Bullock
Habit and leaf form. Shrubs (with densely leafy branches). Leaves whorled; leathery; simple. Lamina entire; linear, or acicular. Leaves exstipulate. Lamina margins revolute.
Leaf anatomy. Hairs present (not stellate).
Stem anatomy. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with fibre tracheids, or without fibre tracheids; with libriform fibres, or without libriform fibres.
Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite. Pollination entomophilous.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in spikes, or in heads. The ultimate inflorescence unit ‘essentially’ racemose. Inflorescences terminal; dense, short or elongate spikes. Flowers leafy bracteate; (bi-) bracteolate; somewhat irregular to very irregular; zygomorphic. The floral irregularity involving the androecium, or involving the perianth and involving the androecium. Flowers cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk absent.
Perianth with distinct calyx and corolla; 9, or 10; 2 whorled; isomerous, or anisomerous. Calyx 5; 1 whorled; gamosepalous. Calyx lobes markedly shorter than the tube to markedly longer than the tube. Calyx campanulate, or tubular; unequal but not bilabiate, or bilabiate, or regular (the two lower segments sometimes more distinct than the three upper); persistent; (sub-) imbricate, or valvate; with the median member posterior. Corolla 4, or 5; 1 whorled; gamopetalous; imbricate; funnel-shaped; sub bilabiate, or regular.
Androecium 4, or 5 (the posterior member being reduced or absolete). Androecial members adnate (epipetalous); all equal, or markedly unequal; free of one another; 1 whorled. Androecium exclusively of fertile stamens, or including staminodes. Staminodes when present, 1; in the same series as the fertile stamens; representing the posterior median member. Fertile stamens representing the posterior median member, the posterior-lateral pair, and the anterior-lateral pair, or the posterior-lateral pair and the anterior-lateral pair. Stamens 4; inserted in the throat of the corolla tube (or between the lobes); not didynamous, not tetradynamous; reduced in number relative to the adjacent perianth, or isomerous with the perianth; oppositisepalous; alternating with the corolla members; filantherous (exserted, the filaments filiform). Anthers dorsifixed; dehiscing via longitudinal slits; introrse; bilocular (the thecae sometimes downwards-divergent). Pollen grains aperturate; 3 aperturate; colporate.
Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 2 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 2 locular. Locules without ‘false septa’. Gynoecium median; stylate. Styles 1 (filiform, exserted); more or less attenuate from the ovary; apical (often excentric). Stigmas 1 (punctiform); simple. Placentation basal. Ovules 1 per locule (or only one of the locules fertile); funicled; ascending; apotropous; anatropous; tenuinucellate. Endosperm formation cellular.
Fruit non-fleshy; dehiscent, or indehiscent; a capsule, or capsular-indehiscent. Capsules when dehiscent, loculicidal and valvular (apically). Seeds endospermic. Endosperm oily. Embryo well differentiated. Cotyledons 2. Embryo straight.
Physiology, biochemistry. Iridoids detected; ‘Route II’ type (+decarb., stilbericoside, cf. Thunbergia). Verbascosides detected (3 genera).
Geography, cytology. Paleotropical and Cape. Sub-tropical to tropical. South Africa.
Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Lamiiflorae; Scrophulariales. Cronquist’s Subclass Asteridae; Lamiales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; lamiid; Order Lamiales.
Species 12. Genera 5; Stilbe, Campylostachys, Xeroplana, Eurylobium, Euthystachys.
These genera are part of the Labiatae/Verbenaceae problem: see remarks under Labiatae.
• Technical details: Stilbe pinastra.
• Technical details: Stilbe albifora, S. ericoides.