Polhillia C.H.Stirt.

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 : 163-165

4.2. Polhillia C.H.Stirt. S Afr. J. Bot. 52: 2 (1986)

Type: Polhillia obsoleta (Harv.) B.-E.van Wyk (= Polhillia waltersii (C. H.Stirt.) C.H.Stirt. )

Plants woody erect or rarely decumbent shrubs, 0.4 — 2.5 m tall, sprouting from woody rootstock. Branches pale brown to green-yellow, glabrescent; lenticels mostly prominent on old stems, sometimes absent; terminal burst branching displayed in some species. Stipules deltoid, bifurcate, fused at least around base or up to more than half their length, sheathing stem, sericeous except in P. involucrata , 1.0 — 10.0 mm long. Leaves alternate, digitately trifoliolate, pubescent (glabrous or rarely sparsely hairy in P. involucrata ), subsessile or rarely shortly petiolate; leaflets conduplicate or flattened, linear to narrowly oblanceolate to oblong-obovate, apex acute-apiculate, base cuneate; margins entire; terminal leaflets, symmetrical, 4.0 — 15.0(— 21.0) X 0.7 — 5.0(— 7.0) mm; lateral leaflets symmetrical, 3.5 — 15.0 X 0.7 — 5.0(— 7.0) mm. In fl orescence 1 — 2(— 5) flowered terminal cluster, subsessile or pseudo-pedunculate, up to 15 mm long; pedicel mostly 2.0 — 7.0 mm long; bract single at base of pedicel, linear-ensiform, sericeous, caducous, 1.0 — 1.5 mm long; ebracteolate. Flowers bright yellow (pink or white in P. involucrata ), 7.5 — 13.0 mm long. Calyx campanulate, 3.5 — 7.5 mm long, bilabiate, lime-green, often flushed maroon-dark pink, shortly sericeous or villous; tube 2.5 — 5.0 mm long; dorsal lip bifid, teeth triangular, 1.0 — 3.5 mm long, fused for less than half their length, apex apiculate-acute; ventral lip trifid, teeth triangular or ensiform, 1.0 — 3.5 mm long, fused for less than half or up to almost their entire length, spreading or converging, apex acute-apiculate or rounded; inner tips of teeth pubescent. Standard 8.0 — 14.0 mm long; claw linear, 2.0 — 4.5 mm long; lamina broadly ovate (ovate or broadly elliptic in P. involucrata ), 6.0 — 11.0 X 5.5 — 14.0 mm, apex emarginate, base cordate (broadly attenuate in P. involucrata ); adaxial pubescence variably spread. Wing petals 7.0 — 12.0 mm long, equal to or slightly longer than keel; claw 2.5 — 4.5 mm long; lamina shape variable, mostly oblong-oblique, 5.0 — 10.0 X 2.8 — 5.5 mm, glabrous or pilose along midline, apex rounded-truncate to acute, base auriculate-truncate, depressions present with lamellate sculpturing, basal-mid above midline. Keel petals 6.5 — 11.8 mm long; claw 2.5 — 4.5 mm long; lamina mostly lunate, 5.0 — 10.0 X 2.8 — 4.5 mm, apex acute-rounded (beaked in P. connata ), pilose mostly along front edge, density variable, base auriculate to truncate, pocket present, basal along midline. Stamens 10, monadelphous; anthers dimorphic, alternating between four long and one carinal, basifixed, and five short, dorsifixed; filaments fused forming staminal tube, slit dorsally, unfused portion spreading to erect, loosely or tightly arranged around style. Pistil 6.4 — 10.7 mm long, subsessile; ovary narrowly oblong, 3.6 — 8.2 mm long, 0.8 — 1.2 mm wide, sericeous, ovules 7 — 12; style terete, erect, usually between 45 — 90̊ angle, height of curvature 1.1 — 5.8 mm, glabrous except basally; stigma regular, capitate. Fruit indehiscent (dehiscent in P. involucrata ), oblong, plicate, partially plicate or non-plicate, laterally compressed between seeds, straight to slightly falcate, tapering toward the apex and base, sericeous to glabrescent. Seed ovate-reniform or squared; testa olive-green to toffee-brown, sometimes almost black, mottled pale orange in P. involucrata and occasionally in P. connata , smooth; hilum round, recessed, sub-terminal; rim aril inconspicuous; micropyle hidden.

4.3. Diagnostic traits

A combination of several characters diagnoses the placement of Polhillia within in the tribe Genisteae . These include flowers singular, flowers borne in terminal clusters, or pseudo-pedunculate (absence of true peduncles). Other SA genistoid genera typically have flowers borne on true peduncles, except for a handful of Argyrolobium species. The two stipules are always fused, at least around the base, and sheath the stem. Other SA Genisteae typically have two unfused stipules that do not sheath the stem. Most Polhillia species have subsessile leaves, while other SA Genisteae genera typically have distinctly petiolate leaves. Polhillia species also lack bracteoles, which are common in other SA Genisteae genera. All Polhillia species, except P. involucrata , have indehiscent fruit, which is unique, as all other SA Genisteae have dehiscent fruit.