Psoralea reticulata C. H. Stirt. & Muasya, 2025

Stirton, Charles H., Bello, Abubakar & Muasya, A. Muthama, 2025, Nomenclatural notes on the genus Psoralea (Psoraleeae, Fabaceae) in South Africa, Plant Ecology and Evolution 158 (2), pp. 168-180 : 168-180

3. Psoralea reticulata C. H. Stirt. & Muasya nom. nov.

Fig. 4

Psoralea carnea E. Mey. ( Meyer 1836: 85), nom. illeg.; non Psoralea carnea (Michx.) Poir. ( Poiret 1804: 694) = Dalea carnea (Michx.) Poir. ( Cuvier 1819).

Otholobium carneum (E. Mey.) C. H. Stirt. ( Stirton 1986: 52), comb. nov. illeg.

Type

SOUTH AFRICA • uncertain locality; Drège s. n.; lectotype (designated by Stirton 1986): MO [ MO 1868216 ]; isolectotypes: P [ P 03496151 , P 03050230 ], G [ G 00022541 ], HAL [ HAL 11940 ], K [ K 000392564 ] fragment .

Diagnosis

Psoralea reticulata is closest to P. heterosepala Fourc. and is a small rounded compact shrub up to 0.6 m tall with sparsely appressed hairy to glabrate, glandular and blackish shoots ( P. heterosepala an erect virgate shrub 1.8–2.5 m tall with virgate, puberulous shoots); stipules broadly triangular, 1.5–1.7 mm long, fused for the length of the petiole and adnate to it ( P. heterosepala stipules triangular, 2–3 mm long, scarious, striate not fused to petiole); standard petals 5.0– 5.5 mm long, very broadly ovate, scarcely auriculate ( P. heterosepala with standard petals 6.0– 6.5 mm long, broadly elliptic; auriculate); calyx with dark green teeth, tube paler green with dark green veins ( P. heterosepala calyx teeth and tube yellowish green, veins hyaline).

Description

Small, erect, deciduous, much branched decumbent reseeding shrub. Stems small, rounded, compact, up to 0.6 m tall. Branchlets terete, slender, sparsely appressed hairy, glabrate, glandular and blackish. Leaves digitately trifoliolate, shortly petiolate, shiny. Leaflets 8–12 × 1.5–2.0 mm, terminal leaflet somewhat longer; very narrowly obovate to oblong, laterals asymmetrical, semi-conduplicate, subsessile to petiolate, base cuneate, apex recurved mucronate, glands not clearly visible, hyaline. Stipules 1.5–1.7 mm long, fused for the length of the petiole and adnate to it, broadly triangular, patent but recurving with maturity, prominently veined, mostly glabrous but with a ciliate margin, persistent. Inflorescences borne on short shoots, axillary, comprising a single triplet of flowers subtended by a 3.5–3.7 × 1.5–1.8 mm pandurate and ciliate bract prominently veined and with irregular apex; the common 1–2 mm long peduncle has a solitary 1.7 mm long, narrowly falcate bract inserted just below the common flower bract. Flowers 7–8 mm long; pedicel 2.0– 2.3 mm long. Calyx equal to or longer than the corolla, 8–9 mm long; lateral and vexillary lobes more or less equal but shorter and much narrower than the very acuminate broadly lanceolate keel lobe; vexillary teeth 1.0– 1.5 mm wide, fused slightly above the tube; sparsely pubescent, margins appressed pubescent; veins raised, very prominent. Standard petals 5.0–5.5 × 4 mm, very broadly ovate, scarcely auriculate, appendages absent; mauve to purple with a largish violet nectar guide and purple netlike veins; claw 1.5–2.0 mm long. Wing petals longer than keel, 6 × 1.5–2.0 mm, auriculate; sculpturing present, upper basal and upper central comprised of up to 20 parallel, transcostal lamellae, rows indistinct. Keel petals 4.3–4.5 × 1.3–1.6 mm, blade bulging, apex rounded; claw 2 mm long. Androecium 3.6–3.7 mm long, sheath split adaxially, tenth stamen free. Pistil 4 mm long; ovary 1 mm long, glabrous, gynophore absent; height of curvature 1.3 mm; style glabrous, 0.3 mm thick at point of flexure; stigma prominent, capitate, penicillate. Fruits 4.5 × 3 mm, beaked; papery, reticulate. Seeds 2.6–2.7 × 2.3–2.5 mm, 1.5 mm thick; dark brown; hilum 0.5 mm long, flushed, very broadly ovate, rim aril present; micropyle deltoid, free from hilum.

Distribution and habitat

Psoralea reticulata has been collected only six times and little is known about its biology. It occurs on the Kouga and Baviaanskloof mountains (Fig. 2 ) in Kouga Sandstone Fynbos (FFs 27; Mucina and Rutherford 2006). We owe its modern rediscovery to the late Elsie Esterhuysen (1912–2006), a renowned plant collector, who traversed the species rich Cape Mountains for so many years with so much success. The discovery of P. reticulata stresses yet again the poor state of collecting along the inland mountains east of Uitenhage and north of the Keurbooms River.

Phenology and ecology

Flowering takes place from May to November. Psoralea reticulata has been found growing in fynbos vegetation on loamy rocky soil.

Etymology

The specific epithet reticulata is a Latin adjective that refers to the large highly reticulately-veined carinal lobe of the calyx.

Preliminary IUCN conservation assessment

Psoralea reticulata has an EOO of 347 km 2 and an AOO of 24 km 2, both classifying it as Endangered. Given that the species has been collected only six times, in five different locations, indicating a potentially small population, the species is hereby assessed as Endangered: EN B 1 ab (iii) + 2 ab (iii) ( IUCN 2012).

Additional material examined

SOUTH AFRICA – Eastern Cape Province: 3323 (Willowmore) • lower slopes near Kouga Peak ; 12 Nov. 1944; Esterhuysen 10187; BOL • Hike from Kouga Wilderness to Pelargonium Cave (– DB); 14 Jun. 2015; Du Preez 50; BOL • Near Smutsberg (– DB); 3 Dec. 2015; Du Preez s. n.; BOL . – Eastern Cape Province: 3324 (Steytlerville) • Scholtzburg, Baviaanskloof (– CA); 17 May 1983; Van Jaarsveld & Kotze 7753; NBG • Baviaanskloof mountains, high ridge to north of Grassnek (– CB); 23 Sep. 2011; Euston-Brown 1334; BOL .

Notes

The exact locality of the type specimen is confused. In his protologue, Meyer (1836) refers to the locality as “ Prout videtur, lecta in regione 111 D ”. However, later in the compilation of Drège’s collecting itineraries ( Drège 1843), the locality 111 D is given as “ Paarl and Paarlberg ” but with no mention of the species being there. As the species is only known from the Kouga and Baviaanskloof mountains, it is clear that there has been a mislabelling. Forbes (1936), in her monograph of Psoralea , confused this species with a group of four other species centred around P. carnea E. Mey. (nom. illeg.). We now recognise these as Psoralea prodiens (C. H. Stirt. & Muasya) C. H. Stirt. , P. heterosepala Fourc. , P. stachyera Eckl. & Zeyh. , and P. acuminata Lam. Psoralea reticulata is separated from these species by a combination of features: small compact deciduous shrub; leaflets conduplicate, glandular, glabrous, shiny, with narrowly obovate to oblong inflorescences on short lateral shoots, 3 - flowered axillary inflorescences; very broadly ovate standard petals; wing petals longer than keel petals; calyx teeth longer than the petals, carinal tooth twice as broad as the rest.

Figures

Figure 2. Known distribution of the six described Psoralea species. Map by Abubakar Bello using QGIS v. 3.28 (QGIS Development Team 2020).

Figure 4. Psoralea reticulata. A. Habit. B. Upper surface of leaflets. C. Flowering shoot. Photographs from iNaturalist: A, B: https://www.inaturalist.org/observations/11141013, Brian du Preez; C: https://www.inaturalist.org/observations/187019589, Nick Helme.