Psoralea margaretiflora (Psoraleeae, Fabaceae): A new species from the Sneeuberg Centre of Floristic Endemism, Eastern Cape, South Africa

Abstract A new species of Psoralea is described. Psoralea margaretiflora C.H. Stirton & V.R. Clark is endemic to the Sneeuberg Centre of Floristic Endemism, Eastern Cape, South Africa. This resprouter is characterised by its small greenish-white flowers with a small trifid purple nectar patch and translucent veins; 5(–7)-pinnate leaflets; multi-branching erect short seasonal flowering shoots; and tall habit of many stiff bare stems with the seasonal shoots massed at the apex. It is most similar to Psoralea oligophylla Eckl. & Zeyh., a widespread species found in the Eastern Cape. The reseeder Psoralea oligophylla differs in its lax virgate spreading habit with numerous long glaucous seasonal shoots; single stem, 1(–3)- glaucous leaflets; more numerous white flowers; and standard petals with a purple ring surrounding a bright yellow nectar patch.


introduction
There are eight species of Psoralea L. in eastern and south-eastern South Africa. Although well-collected and well-represented in herbaria, the known species names are mostly misapplied. These Psoralea species are quite variable and are now in much need of revision following Forbes' (1930) original treatment. P. margaretiflora -the new species described here -was not seen by Miss Helena Forbes, and occurs in the Sneeuberg, in the Eastern Cape Province of South Africa. The Sneeuberg was designated the Sneeuberg Centre of Floristic Endemism by Clark et al. (2009), and P. margaretiflora is the latest addition to a suite of ca. 28 endemics (Goldblatt and Manning 2007, Nordenstam et al. 2009) known from there. Description. Erect resprouter, up to 2 m. Stems 1-30, bare except for seasonal shoots in the upper axils; greyish-brown, covered in white storied lenticels; young seasonal shoots bright green, glabrous, glandular; shoots produced seasonally on old stems, leafy along entire length. Stipules 2-3 (4) mm long, rigid, triangular, semi-patent; longer, green and arching on water shoots; rapidly senescent on flowering shoots. Leaves 7-foliolate at base of each seasonal shoot, 5-foliolate thereafter, glabrous. Leaf size variable, larger (48-55 mm long, 48-60 mm wide) on water shoots from the rootstock; petiole 2-3 (17) mm long. Leaflets of variable length in a leaf; basal pair longest (25-33 mm long), mid-pair shortest (19-26 mm long), and terminal leaflet second longest (18-31 mm long); all 1.0-1.3 mm wide; glabrous, dark green; apex acuminate, base rounded. Peduncles (10) 15-17 mm long, terminated by a tri-toothed cupulum; lower tooth longest, acuminate, upper two teeth fused for half their length; yellowish, rapidly senescent, 1.0-1.2 mm long; pedicels 1-2 mm long. Flowers 10-12 mm long, greenish white, borne 1-5 in leaf axils along flowering shoot. Standard broadly elliptic, 10 mm long, 8 mm wide, claw 3 mm long; greenish-white, nectar flash purple, trifid above the strongly developed auricles. Calyx 5-6 mm long, pale green, glabrous on outside, finely black-haired on inner face of teeth, tube glabrous; teeth and tube equal, teeth triangular, all 3 mm long, carinal tooth cucullate at apex; ribbed, glandular. Wing petals 9-10 mm long, 4 mm wide, claw 3 mm long; locked into keel but not fused; longer than the keel; petal sculpturing present, upper basal, comprising 7-8 transcostal parallel lamellae. Keel petals 6 mm long, 3 mm wide, claw 5 mm long, apex deep purple. Androecium 9 mm long; tenth stamen free; sheath split adaxially, fenestrate. Pistil 9 mm long; ovary 1.5 mm long, stipitate, glabrous; thickened at point of flexure, height of curvature 2 mm, erect, penicillate. Fruits and seeds unknown.

Psoralea margaretiflora
Discussion. Psoralea margaretiflora is characterised by its small greenish white flowers with a small trifid purple nectar patch and translucent veins; 5(-7)-pinnate leaves; erect multi-branching short seasonal flowering shoots and tall habit of many stiff bare stems with the seasonal shoots burst-branching from the apex. It is most similar to P. oligophylla Eckl. & Zeyh., a widespread species found in the Eastern Cape. P. oligophylla, a reseeder, differs in its lax virgate spreading habit with numerous long glaucous seasonal shoots; single stem; 1-3-foliolate glaucous leaves; more numerous white flowers; and standard petals with a purple ring surrounding bright yellow nectar patch.
Two other species occur in the Eastern Cape that might be confused with P. margaretiflora: P. glabra Harv. and P. latifolia (Harv.) C.H.Stirt. The four species can be distinguished as follows: 1a Flowers white or greenish white; standard petal without large white V-shaped nectar patch, veins either translucent or pale violet; wing petals white; calyx glabrous, glaucous or pale green; stipules triangular, flat, erect to semi-patent, not prominent or persistent on old shoots; shrubs up to 3 m tall with many rigid branchless stems bearing clusters of seasonal flowering shoots radiating either terminally from stems or along older shoots giving a broom-like appearance . Distribution and ecology. P. margaretiflora is abundant on the lower and mid-Escarpment slopes (1 200-1 800 m) of the Sneeuberg, Graaff-Reinet District, being concentrated on the Kamdebooberge, Koudeveldberge and Toorberg in the west, and from the Nardousberg to Aasvoëlkrans (behind Pearston) in the east. P. margaretiflora can form dense stands, and is a typical component of riparian thicket/bush vegetation along streams, but is not restricted to such habitats. The vegetation types of which this species inhabits are difficult to classify. It occurs variously in Karoo Escarpment Grassland / "Afromontane Grassland" verging into Mountain Fynbos, and also occurs in closed Otholobium macradenium shrubland. The plant grows primarily on rich turf soils and colluvium associated with dolerite. On the Boschberg -the eastern, wetter end of the Sneeuberg -P. margaretiflora is replaced by P. glabra.
Flowering takes place between October and January but can occur as late as April.
Etymology. The plant name alludes to the appearance of its pearl white flowers as seen in early morning mountain mist and is derived from margaritaceus (L) = pearl-like. Other