Psoralea prompta C. H. Stirt. & Muasya, 2024

Stirton, Charles H., Bello, Abubakar & Muasya, A. Muthama, 2024, Ten new species and notes on the genus Psoralea L. (Psoraleeae, Fabaceae) from South Africa, Plant Ecology and Evolution 157 (3), pp. 291-312 : 291-312

8. Psoralea prompta C. H. Stirt. & Muasya sp. nov.

Figs 2 , 11

Type.

SOUTH AFRICA – Western Cape Province • On Markuskraal dirt road to Paleisheuwel off N 7, along Palmietfontein River , 3218 CD; 32 ° 25 ’ 50.89 ” S, 18 ° 57 ’ 10.86 ” E; 24 Oct. 2009; Muasya & Stirton 4775; holotype: BOL .

Diagnosis.

Psoralea prompta is like P. verrucosa Willd. ex Spreng. within which it was previously included and with which it shares, unusually in Psoralea , multi-flowered shortly pedunculate inflorescences, and partially fused cupulate bracts but differs in its reseeding habit ( P. verrucosa a resprouter); old wood greyish brown with age with white storied lenticels ( P. verrucosa brownish with blotchy lenticels); green shoots and branches smooth with small flushed dimpled-like glands ( P. verrucosa with rough, bluish green shoots and branches covered in distinct raised warty glands); leaves variable, (1 –) 3–5 - foliolate but mostly pinnately trifoliolate, terminal leaflet 70–85 × 4.0– 4.5 mm, laterals 51–60 mm long; flowering shoot leaves 1 - foliolate, 33–45 × 2.0– 2.5 mm ( P. verrucosa leaves pinnately (2 –) 3 - foliolate at base of shoots and on water shoots, 1 - foliolate and smaller thereafter reducing in size up the flowering shoot, terminal leaflet 35–50 (– 55) × 1.0–1.5 (– 3) mm, laterals if present smaller, as are 1 - foliolate leaves); stipules narrowly lanceolate to linear ( P. verrucosa stipules subulate becoming triangular); flowers pale mauve and white ( P. verrucosa flowers dark mauve or purple); wing petals white ( P. verrucosa wing petals mauve).

Description.

Tall floppy tree-like shrub up to 4 m tall, reseeder. Stems 1 to few, arching, branching profusely in upper parts, finely covered in shallow crateriform glands, greasy to the touch, glabrous, glaucous when young, branches forming in tight bunched clusters, becoming woody. Leaves variable, (1 –) 3–5 - foliolate but mostly pinnately trifoliolate, petiolate, stipulate. Leaflets greyish, glabrous, dimpled, flat, apex acute, base rounded, narrowly elliptic to linear-oblong, midrib distinctly keeled below, larger on seasonal shoots than on flowering shoots, terminal leaflet 70–85 × 4.0– 4.5 mm, laterals 51–60 mm long; flowering shoot leaflets 1 - foliolate, 33–45 × 2.0– 2.5 mm; petiole 20–28 mm long, verrucose; petiolules yellow, glabrous. Stipules present, 3–4 × 0.5 mm on flowering short shoots, 7–8 × 1 mm on subtending branchlets, narrowly lanceolate to linear, patent to upcurving, green becoming scarious, glabrous. Inflorescences terminal on short shoots, axillary, pedunculate, scattered along seasonal shoots, 2–7 - flowered per peduncle; peduncle 10–22 mm long, green, dimpled, glabrous. Flowers 12–14 mm long, mauve, bracts absent; scent absent, cupulum imperfect, variable depending on flower congestion, trifid, <1 mm long, well to poorly developed. Calyx lobes 5–7, teeth equal, carinal tooth 2 mm wide, slightly broader than the rest, triangular, glandular, outside glabrous, inside of teeth finely white-haired; teeth and upper part of calyx often flushed purple, vexillar teeth fused for one third their length, tube 2.5–3 mm long, equal to teeth, carinal lobe slightly broader than the rest; vexillar teeth fused above tube for one third their length and somewhat incurved. Standard petals 13–15 × 10–20 mm; claw 2–3 mm long; very broadly ovate, standard petal with purple flush and darker single purple flash, veins darker mauve, reflexed 90–120 ° at anthesis; free swollen white callosities, apex emarginate. Wing petals 10–12 × 4–7 mm; claw 4 mm long; white to pale mauve, longer than keel, cultrate with a broad groove between auricles, strongly folded once along the middle; auricles swollen, well-developed, sculpturing upper basal, comprising up to 5–8 weak curved transcostal lamellae; wings lightly adherent to base of keel. Keel petals 8–13 × 3.5–5 mm; claw 4–5 mm long; blade upcurved, apex acute. Androecium 9–10 m long, apex incurved, tenth stamen free, sheath split adaxially, fenestrate. Pistil 8–9 mm long; ovary 1.5 mm long, stipitate ~ 1 mm long, glabrous, glandular especially near apex, height of curvature 3 mm, thickened at point of flexure, stigma capitate, penicillate. Fruits and seeds unknown.

Distribution and habitat.

Psoralea prompta is a rare species known only from a few collections and from sightings on iNaturalist (Fig. 2 ). It overlaps slightly with P. verrucosa in the north-eastern part of its range. It occurs in seepages and along stream banks between 80 and 280 m a. s. l. within Cederberg Sandstone Fynbos (FFs 4) and can be expected to be found in more patches of this fragmented vegetation type.

Phenology and ecology.

Flowering takes place from October to November.

Etymology.

The specific epithet prompta is derived from the Latin ‘ promptus’ (- a, - um) meaning visible, manifest and refers to its striking colonial habit in an otherwise dry region.

Preliminary IUCN conservation assessment.

No assessment has been made of this species as its distribution is still too uncertain, therefore warranting Data Deficient (DD). However, as it is near roads and consequently the known populations may be quite vulnerable to changes in drainage patterns.

Additional material examined.

SOUTH AFRICA – Western Cape Province: 3219 (Wuppertal) • Biedouw Valley , in stream near a causeway (– AA); 7 Nov. 1982; Stirton & Žantovská 11501; K • Kransvleikloof, Olifants River Mts (– BD); 32 ° 15 ’ 24.99 ” S, 18 ° 50 ’ 02.21 ” E; 29 Oct. 2018; Helme 9347; NBG; https://www.inaturalist.org/observations/17984791 .

Observation.

South Africa, Western Cape Province: Road off Bulshoek Dam, 32 ° 01 ’ 42.74 ” S, 18 ° 49 ’ 45.47 ” E, 12 Dec. 2017, obs. by Joan Kleynhans, https://www.inaturalist.org/observations/17456342.

Figures

Figure 2. Known distribution of the ten described Psoralea species. Map by Abubakar Bello.

Figure 11. Psoralea prompta. A. Shrubs in stream seepage. B. Coppicing shoots. C. Surface of young shoot with papillate glands. D. Shoot with axillary inflorescences in buds and subtending leaves. E. 3 - flowered axillary inflorescence. F. 4 - flowered pedunculate inflorescence showing partially fused lobes of cupulums from individual flowers. G. Apex of a pedunculate inflorescence showing more than one flower emerging from a partially formed cupulum. Photographs: A – G by Charles Stirton.