Polhillia brevicalyx (C.H.Stirt.) B .-E.van Wyk & A.L.Schutte

du Preez, B., Dreyer, L. L., Stirton, C. H. & Muasya, A. M., 2021, A monograph of the genus Polhillia (Genisteae: Fabaceae), South African Journal of Botany 138, pp. 156-183 : 167

1. Polhillia brevicalyx (C.H.Stirt.) B.-E.van Wyk & A.L.Schutte ( Fig. 8 ), Kew Bulletin 44: 3 (1989);

Argyrolobium brevicalyx C.H.Stirt. S. Afr. J. Bot. 50: 4 (1984).

Type: South Africa, Western Cape, 3420 (Bredasdorp): Flats along watercourse 1 km SSE of Uitvlug farm , along road between Bredasdorp and Swellendam , 15 km SW of Swellendam (— AB), 1 Oct 1983, Burgers 3188 ( K, holo.!; STE, now NBG, PRE, iso.!) .

Low growing, rounded, procumbent or decumbent shrub up to 0.5 m tall, often forming wide circular bushes, sprouting from woody rootstock. Branches pale brown, young branches sericeous, older branches glabrescent; lenticels prominent. Stipules 1.0 — 3.0 mm long, green. Lea fl ets narrowly obovate bright green, slightly falcate, glabrous to sparsely hairy adaxially, sericeous abaxially and along margin, conduplicate, apex apiculate, base cuneate, terminal and lateral leaflets equal, 2.5 — 8.0 X 1.0 — 3.0 mm; petiole shorter than lamina, 1.0 — 3.0 mm long. In fl orescence 1 — 3(— 5) flowered terminal cluster, subsessile, pedicel up to 3.0 mm long; bract ± 1.5 mm long, linear-subulate. Flowers bright yellow, 7.5 — 8.5 mm long. Calyx 3.5 — 4.5 mm long, pale green, villous; tube 2.5 — 3.0 mm long; dorsal teeth triangular, ± 1.5 mm long, fused to about half their length, apex acute; ventral teeth narrowly-triangular, ± 1.5 mm long, fused for less than half their length, spreading, apex acute. Standard 8.0 — 8.5 mm long; claw linear, 2.0 — 2.5 mm long; lamina ovate, 6.0 — 6.5 X 5.5 — 7.0 mm, apex emarginate, base cordate; back pilose only along midline. Wing petals 7.0 — 7.8 mm long, equal to or slightly longer than keel; claw ± 2.5 mm long; lamina oblong, 5.0 — 6.0 X 2.8 — 3.0 mm, glabrous, apex obtuse-rounded, base truncate-auriculate, elliptical depression and lamellate sculpturing. Keel petals 6.5 — 7.5 mm long; claw ± 2.5 mm long; lamina obliquely-lunate, 5.0 — 6.0 X 3.0 — 3.5 mm, pilose along fore edge, apex obtuse-rounded, base truncate. Stamens basifixed anthers 0.9 — 1.0 mm long, carinal anther 0.8 mm long, dorsifixed anthers 0.5 — 0.6 mm long; staminal tube 5.6 — 6.2 mm long, unfused portion remaining equidistant from style, sub-erect, neatly arranged around style. Pistil 6.4 — 7.5 mm long; ovary 3.6 — 4.4 X 0.8 — 0.9 mm, ovules 7; style usually at about 80 — 90̊ angle, height of curvature 1.7 — 2.3 mm, glabrous except basally. Fruit indehiscent, non-plicate, green-brown, sericeous, 11.0 — 20.0 X 3.0 — 3.5 mm. Seed ovate-reniform; testa olive-green to brown, smooth, 1.7 — 2.1 X 1.6 — 2.0 mm, 1.4 — 1.7 mm thick.

Etymology

The specific epithet “brevicalyx ” refers to the notably small calyx of this species in comparison with other Polhillia species.

Diagnostic characters

Polhillia brevicalyx is distinguished from all other Polhillia species by its spreading decumbent or procumbent habit (versus erect shrubs in other species); its comparatively small flowers <9 mm long (versus 10 mm or longer in other species); having a distinct petiole (versus leaves subsessile in other species); and seven ovules (versus 9 — 12 ovules in all other species, except P. involucrata with seven ovules).

Distribution, ecology and conservation status

Polhillia brevicalyx flowers from September to October. It is known only from a small area around the type locality ( Fig. 6B ) and grows in small isolated patches extending along a stretch of roughly 6 km. The largest population is found mostly just above the riverbanks of the Sout River on the farm Uitvlug, east of the R319 between Swellendam and Bredasdorp. A thorough population survey located about 180 plants, which is double the number previously recorded ( Raimondo et al., 2009), but it remains critically endangered. This species grows in deep clay in Eastern Ruens ^Shale Renosterveld (FRs 13) bordering on saline Cape Lowland Alluvial Vegetation (AZa 2) ( Mucina and Rutherford, 2006). The Red Data List status of this species is assessed as Critically Endangered (CR B 1ab(iii,v)+ B 2(iii,iv); C2(ii)) following the latest IUCN categories and criteria ( IUCN, 2012).

Additional specimens examined

South Africa. WESTERN CAPE: 3420 (Bredasdorp): Uitvlug Farm, Lower Breede River Valley (— AA), 13 Oct 2003, CREW 31 (NBG); Uitvlugt farm, just off R319 (— AB), 19 May 2017, B. du Preez 280 (BOL); 8 Oct 2017, B. du Preez 353 (BOL); 17 Oct 2017, B. du Preez 395 (PRU); Uitvlugt farm, north of Bredasdorp (— AB), 9 Oct 1986, B.- E. van Wyk 2100 (JRAU), 2101 (JRAU), 2102 (JRAU), 2103 (JRAU); Farm: Uitvlugt, between Bredasdorp and Swellendam, 1 km west of homestead (— AB), 18 Dec 1986, S. Streicher s.n. sub A.L. Schutte 389 (JRAU); Witkop farm behind dam, just north of Uitvlugt (— AB), 17 Oct 2017, B. du Preez 396 (BOL, NBG); Uitvlugt farm, Bredasdorp area (— AB), 26 Nov 2011, Stirton & Curtis 13567 (BOL).

Figures

Fig. 8. Composite plate of Polhillia brevicalyx. 1 — Flower front view; 2 — Flower side view; 3 — Flower bottom view; 4 — Wing petals; 5 — Keel petals; 6 — Androecium (with gynoecium); 7 — Gynoecium; 8 — Fruit; 9 — Close-up view of leaves and stipules; 10 — Habit.Scale bars: 2 mm. Photographs by B. du Preez.

Fig. 6. Map showing distribution of Polhillia in the Western Cape Province, South Africa.A — Distribution of extra Overberg species; B — Species within and just outside of the Overberg region. Note expansion of square in A to map in B.