Psoralea lancifolia 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

5. Psoralea lancifolia C. H. Stirt. & Muasya , nom. nov.

Fig. 6

Otholobium lanceolatum C. H. Stirt. & Muasya , Kew Bulletin 72 (4): article 50, p. 14. 2017. ( Stirton and Muasya 2017).

Psoralea lanceolata (C. H. Stirt. & Muasya) C. H. Stirt. ( Bello et al. 2022: 68), comb. illeg.; non Psoralea lanceolata Pursh ( Pursh 1813: 475) = Ladeania lanceolata (Pursh) A. N. Egan & Reveal.

Type

SOUTH AFRICA – Western Cape Province: 3419 (Caledon) • between Drievlei and Morning View farms ; 13 Jan. 1986; Stirton 11381; holotype: K [ K 003992450 ]; isotypes: MEL [ MEL 223201 ], MO, NBG [ NBG 0147985 -0], PRE .

Diagnosis

Psoralea lancifolia belongs to a small group of resprouting unifoliolate leaved species ( P. dreweae (C. H. Stirt. & Muasya) C. H. Stirt. and P. thomii Harv. ) with racemose inflorescences bearing up to 9 triplets of pedicellate flowers on a peduncle equal to or twice longer than the subtending leaf. This distinctive species is separated from these allied species by the combination of its decumbent habit, thick basal rough woody stems that hug the ground, new terete seasonal shoots commonly black when young with bright yellow pustular glands, oblong inflorescences twice the length of the leaves, white or pale mauve flowers with a purple patch on the upper tip of the keel petals, calyx densely glandular and covered with white patent hairs, calyx teeth blackish, carinal tooth broader and longer than the rest, large white or pale mauve flowers with a purple patch on the upper tip of the keel petals and ovary finely pubescent with forward sloping style.

Description

Small, decumbent, sparsely leaved suffrutex up to 0.2 m tall; resprouting after fires. Lignotuber present, rough, and looks like knotted twisted rope. Stems arising from a short, thickened trunk, up to seven, 90–150 mm long, occasionally branched in one of the lower axils, basal leaves smallest, densely pustulate. Leaves unifoliolate, petiolate, 25–36 × 6–9 (– 10) mm, elliptic, glabrous, cuspidate, mucro straight, apex acute, base cuneate, densely black-punctate when dried, margin glandular, younger leaves glabrous, midrib prominent below, secondary veins on both surfaces raised but less prominent; rachis absent; petiole 2 mm long; petiolule 1 mm long. Stipules 3–5 × 0.5–2 mm, longer than petioles; glabrous, subulate, acuminate, ribbed, glandular. Inflorescences axillary, 1–2 in upper axils, terminating short seasonal shoots, oblong, 25–35 mm long, comprised of 5–9 triplets of flowers with 2–4 mm long pedicels, each set subtended by a flabellate to broadly ovate-oblong, gland-dotted hairy bract, bract caducous; peduncle 25 – 35 mm long, about twice the length of the subtending leaf, densely covered in 0.2 mm high warts. Flowers white or pale mauve, 8–10 mm long, each subtended by a narrowly lanceolate to linear, 3 mm long, caducous bract. Calyx teeth longer than the 2–3 mm long tube, unequal, acute; carinal tooth broadest, 10–11 × 2–2.5 mm, dark green, rest of calyx pale yellowish green; vexillary lobes falcate, same length as the lateral lobes, fused for 1–3 their length above the tube, outer face densely covered in 1.5–2 mm long white patent hairs and many small glands, glabrous on inner face. Standard petals 13 × 8–9 mm, obovate, but oblong when reflexed; white to pale mauve, auriculate, claw 2 mm long, narrowed. Wing petals 10–12 × 3–4 mm, claw 3 mm long, cultrate, upcurving relative to keel, auriculate, longer than and very lightly fused to keel petals; sculpturing upper right central, sometimes upper distal, bottom row intracostal, upper two rows transcostal, each row comprised of up to 25 transverse lamellae. Keel petals 9 × 2.5–3 mm, claw 4 mm long, purple-tipped. Androecium 8 mm long, vexillary stamen free; fenestrate; anthers equal, 0.3 mm long. Pistil 8 mm long; ovary 1.8–2 mm long, tomentose, stipe 1 mm long and glabrous; height of curvature of style 2.5–2.8 mm, thickened before flexure; style forward sloping, sparsely hairy up to entasis; stigma slightly penicillate. Fruits and seeds unknown.

Distribution and habitat

Psoralea lancifolia grows on somewhat clayey stony slopes at the ecotone of sandstone and shale substrates in mesic mountain fynbos at 100–1135 m a. s. l. with a northerly or north-westerly aspect on silcrete – shale substrate in well-drained loamy soil. It occupies the Overberg Sandstone Fynbos vegetation type (FFs 12; Mucina and Rutherford 2006). It is endemic to the northern foothills of Shaw’s Mountain and Karwyderskraal (Fig. 2 ).

Phenology and ecology

It flowers from early November to December and appears to flower from new shoots in only the first year post-fire. Plants will persist above ground for many years. Despite prolific flowering after fires it rarely sets seeds.

Etymology

The specific epithet lancifolia is a Latin word derived from the Latin words “ lancea ” (“ lance, spear ”) and “ folium ” (“ leaf ”) meaning spear-shaped leaves and alludes to the shape of the leaves. It is also meant to retain the meaning of the original name (i. e. narrow-leaved) which is being replaced.

Preliminary IUCN conservation assessment

After three attempts to trace the original locality of Miss Barker’s and Miss Esterhuysen’s first collections of this species, the first author was fortunate in 1986, in the company of Dr Ion Williams (1912–2001), to rediscover it some 5 km away from the Shaw’s Mountain Pass. The new population numbered about 45 plants and was part of a remnant pocket of undisturbed vegetation. Subsequent surveys by the Custodians of Rare and Endangered Wildflowers (CREW) in 2009 discovered another larger colony near the municipal depot in an adjoining property to the type locality. Fortunately, a new population has been found at Karwyderskraal, west of Caledon Mountain on a small rocky outcrop of uncultivated land but which is threatened by agricultural expansion. The two populations are at the two ends of the Babilonstoring Nature Reserve, so it might also occur in remnant patches between them which would be better protected and should be explored. The Shaw’s Mountain Pass locality is now heavily infested with pines and the area is degrading. Raimondo et al. (2009) assessed this species as Critically Endangered: CR B 1 ab (iii, v); C 2 a (i), but incorrectly cited as Esterhuysen 11381 (K) instead of the type Stirton 11381 (K). The species has an EOO of 448 km 2 and AOO of 16 km 2, both classifying it as Endangered. It is collected from three locations. This species is therefore assessed as Endangered: EN B 1 ab (iii, iv) + 2 ab (iii, iv) ( IUCN 2012).

Additional specimens examined

SOUTH AFRICA – Western Cape Province: 3419 (Caledon) • Shaw’s Mt (– AD); 1 Dec. 1951; Barker 7622; NBG • ibid.; 1 Dec. 1951; Esterhuysen 19281; BOL • near the Old Road Works Department camping site, between Drievlei and Morning view farms (– AD); 13 Jan. 1986; Stirton 11100; K, NBG • ibid.; 3 Sep. 2008; Dludlu & Stirton 12; BOL • ibid.; 1 Feb. 2011; Stirton, Muasya & Chimphango 13147; BOL • Steenboksberg, north of Shaw’s Pass, Caledon (– AD); 13 Nov. 2010; Euston-Brown 1077; NBG .

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 6. Psoralea lancifolia. A. Habit and flowering plant. B. Habit and sterile plant. C. Leaves on sterile shoots. D. Inflorescence with pale mauve flowers. E. Prostrate woody stems. Photographs from iNaturalist: A: https://www.inaturalist.org/observations/100630629, Brian du Preez; B, C: https://www.inaturalist.org/observations/73204754, Charles Stirton; D: https://www.inaturalist.org/observations/99517660, user name Linkie; E: https://www.inaturalist.org/observations/73204755, Charles Stirton.