Euphorbia steelpoortensis Bruyns, 2020

Bruyns, Peter V., Klak, Cornelia & Hanáček, Pavel, 2020, A review of the Euphorbia schinzii-complex (Euphorbiaceae) in southern Africa, Phytotaxa 436 (3), pp. 201-221 : 216-218

9. Euphorbia steelpoortensis Bruyns , sp. nov.

This new species differs from E. lydenburgensis and E. pisima by the rhizomatous outer branches, the bluish green to purple-green branches, the shorter spines and the shorter stipular prickles.

Type:— SOUTH AFRICA. Limpopo: Steelpoort distr., turnoff to Penge, 20 August 1973, Nel 337 (holotype NBG!). Fig. 8 , 9 .

Bisexual succulent 0.1–0.3(–0.4) × 0.15–0.5 m, with outer branches often rhizomatous. Branches 50–300 × 5–12(–15) mm, smooth, bluish to purplish green; tubercles in decussate pairs fused into 4 occasionally somewhat rounded angles with surface slightly concave to slightly convex between angles, with spine-shields 4–8(–9) mm long, 1–2 × 2–3 mm above spines and 1–4(–5) mm long and often ± equally broad below spines as above, remaining well separated, spines 3–8(–12) mm long; leaf-rudiments ± 1 × 1–1.5 mm, with minute brown stipular prickles ± 0.5 mm long. Synflorescences many per branch usually towards apex, each a solitary cyme in axil of tubercle, on short peduncle ± 1 mm long, each cyme with 3 transversely disposed cyathia, central male, lateral 2 bisexual and developing slightly later each on peduncle ± 2 mm long and thick, with 2 ovate bracts ± 1 × 2 mm subtending lateral cyathia; cyathia shallowly cupular, glabrous, 3.5–5 mm broad (1.5 mm long below insertion of glands), with 5 pale yellow obovate lobes with deeply incised margins, bright yellow; glands 5, transversely rectangular to nearly square and contiguous, ± 2 mm broad, bright yellow, ascending-spreading, inner margins flat, outer margins entire and slightly ascending, surface between two margins dull; stamens glabrous, bracteoles enveloping groups of males, with finely divided tips, glabrous; ovary obtusely 3-angled, glabrous, slightly reddish green near top, raised on pedicel 1–1.5 mm long; styles 1–3 mm long, branched to just above base. Capsule 3–4 mm in diam., obtusely 3-angled, glabrous, slightly raised ± 2 mm inside remains of cyathium and peduncle elongating to 2–5 mm.

Distribution & Habitat: — Euphorbia steelpoortensis is mainly found in the valley of the Olifants River from around Steelpoort and Burgersfort to near Chuniespoort, with an outlying population along the ridge of the Strydpoort Mountains south-west of Haenertzburg. Plants grow among rocks and bushes in stony ground in the valleys but may also occur on steep slopes among tufts of grass or in shallow pockets of soil in outcrops of dolomite ( Fig. 8 ).

Discussion: —Plants that occur in low-lying areas have a rhizomatous habit with branches to 20 cm long, while those from high elevations in the Strydpoort Mountains are hardly rhizomatous at all and have short branches, rarely more than 5 cm tall. In all of them the branches are grey-green, which makes them easy to distinguish from E. lydenburgensis and from E. pisima . In some populations of E. steelpoortensis the branches are relatively rounded, with low tubercles (e.g., Bruyns 12062 (BOL)) and these may look considerably like E. aeruginosa , but they differ from E. aeruginosa in the longer pedicel under the female florets. In E. steelpoortensis the spine-shields are often more or less elliptical and are sometimes short below the spines. Florally E. steelpoortensis differs from both E. aeruginosa and E. pisima by the fact that the cyathia are slightly more raised ( Fig. 9 D ) and the peduncle beneath the cyathium may elongate later to raise the capsule 2–5 mm above the branch. From E. aeruginosa it differs as well by the longer pedicel of the female floret ( Fig. 9 G, H ).

Additional specimens examined: — SOUTH AFRICA. Limpopo: 10 miles east of Chuniespoort Police Stn (2429BA), Acocks 12912 (PRE). Jaglust (2429BA), 1020 m, Bruyns 12062 (BOL). Near Chuniespoort (2429BA), 1000 m, Marloth 5145 (K). North side of Olifants River, east of Malipsdrift (2429BB), Van der Merwe 2167 (PRE). East of Malipsdrift (2429BB), 710 m, Bruyns 12114 (S). La Fleur, Wolkberg (2429BB), 1750 m, Winter 5196 (NBG). 9 miles east of Chuniespoort (2429BC), 3000’, Codd 1700 (K). Sekukhune, Radingwana Village (2429DB), Becker & Möller 1075a (UNIN). Steelpoort (2430CA), 2600’, Leach 11692 (NBG); Herre sub SUG 7188 (BOL). 15 km south of Penge (2430CB), Hardy & De Villiers 6013 (K). Bridge over Steelpoort River, Burgersfort (2430CB), 2100’, Smuts & Gillett 3523 (PRE). ± 1 km from Burgersfort towards Steelpoort (2430CB), Van Wyk et al. 13194 (PRU). Burgersfort (2430CB), Van der Merwe 1006 (K). Grootboom, near Steelpoort (2430CC), 900 m, Kluge 2451 (NBG). Tafelkop, 5 km NE of Groblersdal (2529AB), Leach 11685 (NBG). Rhenosterhoek, Loskop Dam (2529AD), Theron 1464 (PRE). Hammond’s Mine, Roossenekal (2529BB), 4000’, Dahlstrand 1871 (PRE).

Figures

FIGURE 8. Distribution of Euphorbia steelpoortensis.

FIGURE 9. Euphorbia steelpoortensis. A, young spines and leaf-rudiment from above (scale 2 mm, as for B–E). B, young spines and leaf-rudiment from side. C, spine-complex from above showing shape of spine-shield (dotted line). D, side view of part of cyme in female stage. E, face view of cyathium in late male stage. F, anthers and bracteole (scale 1 mm, as for G, H). G, H, female floret. Drawn by P. Bruyns from:A–G, Bruyns 13555, Burgersfort, Olifants River Valley, South Africa; H, SW of Haenertsburg, Winter 5196 (NBG).