| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Stilbaceae Kunth

~ Verbenaceae.

Including Stilbeaceae Bullock; excluding Retziaceae.

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).

Axial (stem, wood) anatomy. Internal phloem absent. Secondary thickening developing from a conventional cambial ring.

The axial xylem with fibre tracheids, or without fibre tracheids; with libriform fibres, or without libriform fibres; including septate fibres. ‘Included’ phloem absent.

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 units ‘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, apically loculicidal and valvular. Seeds endospermic. Endosperm oily. Embryo well differentiated. Cotyledons 2. Embryo straight.

Physiology, phytochemistry. Verbascosides detected (3 genera). Iridoids detected; ‘Route II’ type (+decarb., stilbericoside, cf. Thunbergia).

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 III core angiosperms; core eudicot; Superorder Asteranae; lamiid. APG IV Order Lamiales.

Species 12. Genera 6; Stilbe, Campylostachys, Xeroplana, Eurylobium, Euthystachys, Kogelbergia.

General remarks. These genera are part of the Labiatae/Verbenaceae imbroglio: see remarks under Labiatae.

Illustrations. • Kogelbergia verticillata (as Stilbe mucronata): Hook. Ic. Pl. 26 (1899). • Le Maout and Decaisne: Stilbe pinastra. • Le Maout and Decaisne: Stilbe albifora, S. ericoides. • Xeroplana zeyheri: Briquet, Bull. de l'Herbier Boissier 4 (1896).

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: 8th June 2026. delta-intkey.com’.

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