Polhillia obsoleta (Harv.) B.-E.van Wyk

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 : 170-171

4. Polhillia obsoleta (Harv.) B.-E.van Wyk ( Fig. 12 ), Bothalia 22: 1 (1992).

Argyrolobium obsoletum Harv. Flora Capensis 2: 70 (1862).

Type: Cape, without precise locality, Thunberg s.n. sub UPS-THUNB 16504 ( UPS, holo.!) .

Aspalathus sericea sensu Thunb. Flora capensis 574 (1823) non DC.

Lebeckia waltersii C.H.Stirt. Bothalia 13: 3 — 4 (1981). Polhillia waltersii (C.H.Stirt.) C.H.Stirt., S. Afr J. Bot 52: 4 (1986).

Type: South Africa, Western Cape, 3319 (Worcester): Worcester commonage 1.5 miles north-west of town (— CB), 30 Jul 1975, Rourke 1484 (K, holo.!; NBG, iso.!).

Erect, rounded shrubs up to 1.5 m tall, with many erect stems sprouting from a woody rootstock. Branches pale green-brown to golden, aging brown; lenticels prominent on old stems; with terminal burst branching. Stipules 1.0 — 3.5 mm long, green. Lea fl ets narrowly oblanceolate, blue-green, sericeous, partially conduplicate, apex acute, base cuneate, terminal leaflet 4.0 — 11.0(— 16.0) X 1.0 — 2.5 (— 3.5) mm, lateral leaflets 3.5 — 10.5(— 15.0) X 1.0 — 2.5(— 3.5) mm; leaves subsessile. In fl orescence 1 — 2 flowered terminal cluster, pseudo-pedunculate up to 8.0 mm long; pedicel 2.0 — 3.0 mm long; bract ± 1.0 mm long, linear. Flowers yellow, 10.0 — 11.0 mm long. Calyx 3.5 — 4.0 mm long, lime-green, sometimes flushed maroon, shortly sericeous; tube ± 2.5 mm long; dorsal teeth broadly triangular, 1.0 — 1.5 mm long, fused for less than one third of their length, apex apiculate-acute; ventral teeth triangular, 1.0 — 1.5 mm long, fused for ± half their length, spreading, apex acute. Standard 9.5 — 11.0 mm long; claw linear, ± 3.5 mm long; lamina broadly ovate, 6.5 — 8.0 X 9.5 — 11.0 mm, apex emarginate, base cordate; back shortly sericeous only on and around apical half of midline. Wing petals 9.0 — 10.0 mm long, equal to or slightly longer than keel; claw 3.5 — 4.0 mm long; lamina obliquely oblong, 7.5 — 8.0 X 3.0 — 4.0 mm, glabrous, apex rounded-truncate, base auriculate, triangular and oblong depression with lamellate sculpturing. Keel petals 8.5 — 9.5 mm long; claw 3.5 — 4.0 mm long; lamina broadly-lunate, 6.5 — 7.5 X 3.2 — 3.8 mm, pilose along fore edge, apex obtuse, base rounded-auriculate. Stamens basifixed anthers 1.3 — 1.4 mm long, carinal anther 1.1 — 1.2 mm long, dorsifixed anthers 0.7 mm long; staminal tube 6.9 — 8.0 mm long, unfused portion spreading somewhat, sub-erect, loosely arranged around style. Pistil 8.1 — 9.0 mm long; ovary 5.5 — 6.3 X 1.0 mm wide, ovules 12; style usually at about 80̊ angle, height of curvature 2.6 — 2.8 mm, glabrous except basally. Fruit indehiscent, plicate, straight to slightly falcate, woody, sericeous between folds, sericeous to glabrescent elsewhere, yellowish green turning russet brown-chestnut, 16 — 23 X 3.0 — 4.0 mm. Seed ovate-reniform; testa olive-green to toffee-brown, sometimes finely brown-dotted, smooth, 1.7 — 2.5 X 1.6 — 2.2 mm, 1.4 — 1.9 mm thick.

Etymology

The origin of the specific epithet “obsoleta ” is unknown as Harvey (1862) did not provide an explanation when he described it as Argyrolobium obsoletum Harv. It could be from the Latin “ obsoletus ” meaning worn out or decayed, based on the poor condition of the type specimen.

Diagnostic characters

Polhillia obsoleta is morphologically most similar to P. ignota , but is best distinguished by its blue-green leaves (versus bright green leaves); pseudo-peduncles that are up to 8.0 mm long bearing one or two flowers (versus pseudo-peduncles up to 15 mm long with up to four flowers); mature fruit russet brown and pubescent-glabrescent (versus mature fruit pale brown and densely pubescent); ventral calyx teeth spreading (versus ventral calyx teeth converging); wing petals obliquely oblong with two dorsal basal-mid depressions (versus wing petals lunate with three dorsal basal-mid depressions). The geographical distribution of this species is also distinct, as it occurs only in the Breede River valley around Worcester, whereas P. ignota only occurs in the Swartland.

Distribution, ecology and conservation status

Polhillia obsoleta flowers from June to August, with an odd record in February. It is endemic to a small area around the town of Worcester in the Breede River valley ( Fig. 13 ). Much of its former habitat has been lost to the expansion of the town and it remains threatened by further development. This species is now restricted to a few fragments of Breede Alluvium Renosterveld (FRa 1) along the urban fringe of Worcester ( Mucina and Rutherford, 2006). The largest remaining population is at the Worcester Airfield, which is home to roughly 500 plants. A smaller population of roughly 200 plants occurs just south of the N1 highway. This area is proposed to be formally conserved as a conservation offset for a nearby development, thus offering this species some protection from future development. The Red Data List status of this species is assessed as Endangered (EN A2c; B 1ab(iii,v)+ B 2ab(iii,v)) following the latest IUCN categories and criteria ( IUCN, 2012).

Additional specimens examined

South Africa. WESTERN CAPE: 3319 (Worcester): Worcester commonage 1.5 miles NW of town (— CB), 30 Jul 1975, Rourke 1484 (NBG); 22 Feb 1981, C.J. Burgers 2636 (NBG); Veld near Worcester drive-in cinema (— CB), 15 Nov 1980, I. B. Walters 1919 (NBG); 10 Sept 1976, I. B. Walters 1507 (NBG); 24 Jul 1975, I. B. Walters 190 (NBG); 20 Sept 1976, I. B. Walters s.n. sub NBG113326 (NBG); 17 Jul 1981, I. B. Walters 1918 (NBG); 5 Feb 1980; B.- E. van Wyk 204 (NBG); Worcester West (— CB), 10 Jul 1975, I. B. Walters 58 (NBG); New golf club house site (— CB), 28 Aug 1985, Bayer & Forrester 4904 (NBG); Worcester turn-off from N1 (— CB), 6 Aug 2003, Manning 2847 (NBG); Worcester C.P. (— CB), 19 Jul 1962, I. B. Walters 7 (NBG); 27 Jul 1968, I. B. Walters 7 (NBG); Worcester airfield, near hangers (— CB), H. M. Walters 623 (NBG); Worcester airfield, between runways (— CB), 21 Apr 2017, B. du Preez 277 (BOL, PRE); 30 Jul 2017, B. du Preez 306 (BOL, PRE); Worcester, veld between N1 and water reservoir (— CB), 1 Nov 2007, Cowell, Bennett & Pekeur 3554 (NBG); Worcester (— CB), 12 Oct 2009, Muasya, Stirton & Curtis 4104 (BOL); 4 Jul 1987, B.- E. van Wyk 2701 (JRAU); Near Worcester (— CB), 28 Sept 1978, Esterhuysen 35048 (BOL); Worcester, S of N1 and west of mall (— CB), 8 Aug 2018, B. du Preez 523 (BOL, PRU); 18 Sept 1981, Stirton 9134 (PRE).

Figures

Fig. 12. Composite plate of Polhillia obsoleta. 1 — Flower front view; 2 — Flower side view; 3 — Flower bottom view; 4 — Wing petal; 5 — Keel petal; 6 — Androecium; 7 — Gynoecium; 8 — Fruit;9 — Close-up of leaf and stipules; 10 — Habit. Scale bars: 4 mm. Photographs by B. du Preez

Fig. 13. Distribution of Polhillia obsoleta