Psoralea luteovirens 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

7. Psoralea luteovirens C. H. Stirt. & Muasya sp. nov.

Figs 2 , 9 , 10

Type.

SOUTH AFRICA – Western Cape Province • Vensterklip Farm between wind pump and Vensterklip , 3218 (– AD); 32 ° 16 ’ 52.50 ” S, 18 ° 25 ’ 08.55 ” E; 19 Nov. 2017; Ibrahim 1427; holotype: BOL; isotypes: NBG, K, L, MO, PRE .

Diagnosis.

Species similar to Psoralea glaucescens Eckl. & Zeyh. sharing such features as having an unstable and variable number, length, and insertion of leaflets but differs in its large untidy open shrubby habit with 1 - few smooth greyish brown stems ( P. glaucescens a densely compact hemispherical shrub arising from multiple grey stems with rough bark); absence of seasonal burst-branching ( P. glaucescens with seasonal burst branching from tips of previous seasonal shoots); leaves green, (3–4 –) 5–6 - foliolate ( P. glaucescens glaucous, 3 – (4 –) 5 - foliolate reducing to 1 - foliolate in flowering shoots); flowering sparse ( P. glaucescens flowering profuse); flowers 1 (– 2) borne in axillary axils subtended by 5 - fid leaflet ( P. glaucescens with 1–3 flowers per axil borne by a 1 - foliolate leaflet); and standard petal white, with small purple flash, green in upper parts paling towards the margins, veins not discoloured ( P. glaucescens creamy yellow, tinged green, with a long central purple flash and veins).

Description.

Large untidy shrub up to 2 m tall and wide. Stems 1 - few; branches many, glabrous, rigid; seasonal shoots green, striped, rounded with 4–5 angles in cross-section, finely yellow striped, glandular but glands below the surface, old wood brown. Leaves (3–4 –) 5–6 - foliolate. Leaflets very variable in number, length and insertion, upper three leaflets digitate, (10–15 –) 30–45 × 2 mm, becoming shorter towards apex of shoots, linear, dark green, glabrous, laterally compressed, apex rostrate; densely glandular (translucent), glands impressed, persistent; rachis 5–7 mm long, green, glabrous; petiole (5 –) 7–10 (– 15) mm long. Stipules subulate, 1 - nerved, green with orangey glands, tips acute, 2–3 mm long, rapidly senescent then recurving. Inflorescences are borne in most upper axils of seasonal shoots with 1–3 flowers per axil and often an aggregate of many very short side branches off the main axis with up to 5 axils with flowers; buds green with purple midline, glabrous; peduncles present, 12–20 mm long, paired free basal bracts minute, triangular; pedicels 2–3 mm long; cupulum bifid, with one of the teeth cleft, teeth equal, triangular, acute, glabrous, 3 mm long, situated at the apex of the peduncle, dotted with small orange glands. Flowers 14–15 mm long; axillary, 1–3 per axil, patent, yellowish green and white, veins not discoloured; maturing sequentially up the shoot; faintly sweet-scented. Calyx glabrous, lobes subequal, with keel tooth 2 mm longer and twice broader than other 4 teeth; longer than 4 mm long calyx tube; carinal tooth 6–7 mm long, broadly ovate, acute, cucullate; vexillar calyx lobes fused just above the tube; calyx shorter than corolla; inner face of calyx teeth finely covered in white hairs, margins finely ciliate; vexillar teeth green; all teeth strongly ribbed; glands numerous, prominent, glands mostly constant in size, same density all over, drying orange. Standard petal 10–13 × 13 mm; broadly ovate, green in upper parts paling towards the margins, nectar patch a small narrow 2 mm long purple central strip arising between the two free vertical 2 mm long narrow white swollen appendages above the claw, veins hyaline; auricles well-developed, almost tubular when pressed together at anthesis; apex emarginate; claw 3 mm long. Wing petals 12 × 5 mm, longer than keel petals; claw 4 mm long; white, broadly cultrate, straight, tips folded inwards but not touching when viewed from front, furrowed from auricle to tip; sculpturing present, upper basal, with up to ten parallel transcostal lamellae; not fused to keel petals near base. Keel petals 10 × 6 mm; claw 4 mm long; white, apex rounded, purple-tipped. Androecium 10 mm long, tenth filament mostly free but slightly adherent towards base, fenestrate, nectarial ring present. Pistil 10 mm long, ovary 2 mm long, pedicellate, gynophore 0.5 mm; covered all over with short-stalked club-shaped glands; style filiform, scarcely swollen, sharply recurved, height of curvature 4 mm, stigma capitate, penicillate. Fruits known only at immature stage, narrowly obovate, strongly reticulate, chartaceous, brown. Seeds kidney-shaped, hilum central, elliptic, black.

Distribution and habitat.

Psoralea luteovirens is endemic and restricted to low hills in the Verlorenvlei area at 80–180 m a. s. l. in Graafwater Sandstone Fynbos (FFs 2) on conglomerate rocky areas growing in cracks in rocky slabs surrounded by Lamberts Bay Strandveld (FS 1) whereas P. glaucescens is a montane species distributed in the Richtersveld, Kamiesberg, Bokkeveld, and Matsikamma Mountains (Fig. 2 ).

Phenology and ecology.

Flowering takes place from November to December.

Etymology.

The specific epithet luteovirens (Latin ‘ luteus’ = yellow and ‘ virens’ = green) refers to the distinctive yellowish-green colour of the flowers.

Preliminary IUCN conservation assessment.

This species is poorly collected, known from a single locality. It has a narrow distribution range and a small area of occupancy (<10 km 2), in an area under increased conversion into agriculture, hence based on the IUCN criteria ( IUCN 2012) its present status corresponds to Critically Endangered: CR B 2 ab (i, ii, iii, iv, v).

Observations.

South Africa, Western Cape Province: Vensterklip, NE of Elandsbaai, 32 ° 16 ’ 52.39 ” S, 18 ° 25 ’ 08.47 ” E, 15 Jan. 2020, obs. by Brian Du Preez, https://www.inaturalist.org/observations/37366554; Vensterklip, NE of Elandsbaai, 32 ° 16 ’ 54.23 ” S, 18 ° 25 ’ 07.1 ” E, 21 Nov. 2019, obs. by Brian du Preez, https://www.inaturalist.org/observations/37366539; Vensterklip Farm, Clanwilliam District, 32 ° 16 ’ 50.99 ” S, 18 ° 25 ’ 09.98 ” E, 21 Nov. 2019, obs. by Petra Broddle, https://www.inaturalist.org/observations/18774301; Verlorenvlei, Vensterklip Farm, 21 Nov. 2019, obs. by Gigi Laidler, https://www.inaturalist.org/observations/18774301.

Figures

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

Figure 9. Psoralea luteovirens. A. Habit and habitat of shrub, with seasonal shoots, growing in a fissure on a rocky outcrop on a hill. B. Habit and habitat of older plant on plateau of hill. C. Bark. D. Terminal shoot showing flower buds. E. Side view of a flower in axil with subtending leaf. F. Stipules. G. Frontal view of flower. H. Papery, rugulate pericarp of fruit with persistent style. I. Seed. Photographs: A, E – I by Brian du Preez; B – D by Ismail Ibrahim.

Figure 10. Psoralea luteovirens. A. Habit. B. Terminal branch at end of season. C. Bark of old stem. D. Side view of mature flower. E. Stalk and cupulum at the apex. F. Lobes of cupulum opened out. G. Frontal view of flower. H. Standard petal showing auricles and appendages. I. Wing petal with folded midline and prominent auricle. J. Keel petal. K. Pistil. L. Stigma. M. Nectarial ring. N. Calyx opened out with larger carinal lobe on left. O. Variation in leaflets. P. Tip of terminal leaflet. Q. Transverse section through leaf. R. Flower bud. S. Seed. T. Rugulate pericarp of fruit with persistent style. U. Stipules. Artist: Charles Stirton.