Acanthopsis tetragona H. M. Steyn 2017, sp. nov.
Creators: name: Steyn, Hester M.
name: Van Wyk, Abraham E.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Lamiales
Acanthaceae
Acanthopsis
Acanthopsis tetragona

description: 3. Acanthopsis tetragona H.M.Steyn, sp. nov.   
 Type: — SOUTH AFRICA. Northern Cape: Namaqualand District, Richtersveld, S of Sunvalley camp site, 588 m, (2817 CB), 8 August 2011, Steyn 1848 (holotype PRE0861471 -0!; isotype NBG!).   
 Diagnosis: — Acanthopsis tetragon a differs from A. glauca in bracts being short-spined (not with excurrent spines up to 20 mm long), long, viscid glandular hairs (not short, eglandular hairs), inflorescences thicker, (12–)14–16(–20) mm (not 8–10 mm) in diameter and from A. dregeana in being a compact subshrub 12–20 cm tall (not a shrublet 20–40 cm tall).   
Perennial subshrub, (8–) 12–20 cm tall. Leaves sessile; lamina oblanceolate, 40–70(–75) × (8–) 10–15 mm, with appressed to strigose short, white hairs and subsessile glands; base attenuate, often decurrent; margin undulate, dentate-spinose to coarsely dentate-spinose, spines rigid (2–)4–6(–8) mm long, yellowish or maroonish brown; apex cuspidate. Inflorescences subsessile to shortly pedunculate, cylindrical to turbinate, 40–110 mm long (excluding peduncle), (12–)14–16(–20) mm in diameter. Bracts ovate to obovate, (22–)23–28(–30) mm long, lamina (12–) 13–18 mm long; lower bracts ending in 5(–7) primary spines, central primary spine nearly always simple; middle to upper bracts with 3(–5) primary spines, usually ending in 3 broadly triangular to ovate, mucronate lobes with 3 main central veins usually converging towards tip of central primary spine, central primary spine usually to nearly always simple or with 2 pairs of very short, marginal secondary spines, primary spine tips usually recurved in fruit; lower bracts hirsute with deflexed to spreading short, white hairs; middle to upper bracts with spreading short, white hairs together with long, viscid glandular hairs, lamina often with long, spreading silky hairs, usually also with glandular hairs adaxially. Bracteoles narrowly lanceolate to linear, (5–) 6–7 mm long, silky-hairy, also with glandular hairs. Calyx with dorsal sepal ovate, acuminate to cuspidate, (11–) 12–13 mm long, silky-hairy, also with long, glandular hairs abaxially, especially towards tip, 5–7-veined from base; ventral sepal ovate, (11–) 12–13 mm long, silky-hairy, also with long, glandular hairs abaxially, especially towards tip, 5–7-veined from base; lateral sepals lanceolate, ending in spinous tip, broader at base, 7–8 mm long, densely silky-hairy, also with glandular hairs. Corolla blue-purple or lilac with lemon-yellow throat, (25–)26–27(–30) × 9–11 mm, tube (8–) 9–11 mm long; central lobe broader than long or equal, constricted at base, truncate to emarginate. Filaments 5–7(–8) mm long, glandular; anthers beige, 2–3 mm long. Style with patch of glandular hairs at base. Capsules ovate, flattened, glabrous, shiny, 7(–9) × 3(–4) mm. Seeds ovate, 6 × 5 mm, covered with long white hygroscopic hairs.  
 Etymology: —The specific epithet “ tetragona ” refers to the regular decussate arrangement of the bracts that gives the inflorescence a distinctly “four-angled” appearance when viewed from above.
description: Published as part of Steyn, Hester M. & Van Wyk, Abraham E., 2017, Taxonomic notes on Acanthopsis Harv. (Acanthaceae, tribe Acantheae): the group with trifid bracts, pp. 201-217 in Phytotaxa 295 (3) on page 212, DOI: 10.11646/phytotaxa.295.3.1, http://zenodo.org/record/13688365