Rhynchosia waterbergensis Ajao, Boatwr. & Moteetee, 2018

Ajao, Abdulwakeel Ayokun-Nun, Boatwright, James Stephen & Moteetee, Annah Ntsamaeeng, 2018, Rhynchosia waterbergensis (Cajaninae, Phaseoleae, Fabaceae), a new unifoliate species from Waterberg, South Africa, Phytotaxa 382 (2), pp. 234-238 : 235-236

Rhynchosia waterbergensis Ajao, Boatwr. & Moteetee , sp. nov. ( Fig. 1 )

The species is similar to R. spectabilis in that the whole plant is canescent–tomentose, the leaves are broadly ovate or ovate-orbicular, and the standard petals are pubescent. It differs in having unifoliate leaves (trifoliolate in R. spectabilis ), 4–8-flowered inflorescence (opposed to 2–5-flowered) that is longer (25–60 mm, compared to 18–30 mm) and sometimes branched. The calyx lobes are also shorter (upper lobes 1 mm vs 2–3 mm, lateral lobes 2–3 mm opposed to 3–5 mm, carinal lobes 4–5 mm vs 5–7 mm). Contrasting morphological characters separating the two species are presented in Table 1.

Type: — SOUTH AFRICA. Limpopo Province, 2428 (Waterberg): 12 miles (19.3 km), North East of Nylstroom [Modimolle] (- BC), December 3, 1946, Story 1543 (holotype PRE!).

An erect subshrub of about ± 75 cm in height, stem much branched, whole plant greyish to white canescent-tomentose. Stipules lanceolate, canescent-tomentose, 2–4×0.5–1.0 mm; petiole 5–10(12) mm long; leaves alternate, unifoliolate, canescent-tomentose, broadly ovate or orbicular-ovate, reticulate veins prominent on both surfaces, adaxial surface greyish-brown, abaxial surface greyish, glands yellowish-brown usually situated under the hairs on both surfaces, margin entire, 30–59× 20–52 mm, tip acute, base slightly cordate. Inflorescences are axillary and sometimes branched at the apex, 25–60 mm long, occasionally longer than the leaves, 4–8-flowered if the inflorescence is branched and usually 4-flowered if not, peduncle (12) 20–40 mm long, slightly robust, canescent-tomentose; pedicels 1–3 mm long,; bracts lanceolate, 2–3×0.5–1.0 mm, bracteoles lanceolate, 3–5×0.5–1.0 mm, usually longer than the bracts. Flowers large, 12–15 mm long, yellow. Calyx bilabiate, ± 6–9 mm long, tomentose or pubescent, slightly glandular, tube 2–3 mm long; calyx lobes unequal, acuminate; upper lobes connate to almost the top, ± 1 mm long, lateral lobes 2–3 mm long, carinal lobe longer than the lateral lobes, ± 4–5 mm long. Standard obovate, 11–13× 9–10.5 mm, pubescent, slightly glandular especially at the base close to the claw, apex emarginate, base hastate-sagitate, claw linear, 2–4 mm long; wings 8–10× 3 mm, oblong, spurred at the base, with broad sculpturing, claw linear, 3–4 mm long; keel somewhat rostrate or boat shaped, 9–10× 4–6 mm, wider than the wings, pocketed, claw linear, 3–5 mm long. Androecium diadelphous with nine filaments fused and the vexillary stamen free to the base, 12–14 mm long, tube 1.5–2.0 mm long, anthers monomorphic, dorsifixed; gynoecium 4–6×0.6–1.0 mm, oblong-elliptic, shortly stipitate or subsessile, pilose or densely pubescent, 2-ovuled; style 10–12 mm long pubescent, curved upwards. Fruit and seed not seen.

Phenology: —Based on the specimens examined, the species is found flowering in October and December with mature flowers which implies that it starts flowering earlier than October and possibly beyond December.

Distribution and ecology: —The species favours rocky wooded slopes and quartzite ground between 4000–4500 m above sea level. It occurs in the northeastern part of Modimolle, Waterberg Massif, Limpopo Province, South Africa ( Fig. 2 ).

Notes: — R. waterbergensis is also similar to R. monophylla Schltr (1897: 279) in having unifoliolate leaves but the later differs in the stem that is trailing and pubescent (erect and canescent-tomentose in R. waterbergensis ), pubescent leaflets and 1–3-flowered inflorescences (opposed to canescent-tomentose leaflets and 4–8-flowered inflorescences in R. waterbergensis ). R. waterbergensis appears only to occur in the Modimolle (Nylstroom) area.

Specific name etymology: — The specific epithet is derived from the district in which the plant was collected, i.e. ‘Waterberg’.

Additional specimens examined: — SOUTH AFRICA. Limpopo, 2428 (Waterberg): 12 miles (19.3 km), North East of Modimolle [old road] (- BC), December 3, 1946, Codd 2258 ( PRE) ; about 8 miles (12.9 km), from Modimolle on Naboomspruit road (- BC), October 17, 1956, Meeuse 9735 ( PRE) .

Figures

FIGURE 1. Rhynchosia waterbergensis A, Habit showing unifoliolate leaves. B, Outer surface of calyx (upper lobes to the left). C, Standard petal. D, Keel petal. E, Wing petal. F, Androecium G, Gynoecium. H, Bract. I, Bracteole. Voucher specimens. A, Story 1543 (PRE). B-I, Meeuse 9735 (PRE). Scale bar; A = 10 mm, B-I= 1mm.

FIGURE 2. Known geographical distribution of Rhynchosia waterbergensis.