Euphorbia pisima 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 : 210-212

7. Euphorbia pisima Bruyns , sp. nov.

This new species differs from E. lydenburgensis by the slender branches forming low, dense clusters. It differs from all other members of the E. schinzii -complex by the longer pedicel beneath the female floret.

Type:— SOUTH AFRICA. Limpopo: 34 km north-east of Ohrigstad, 1000–1100 m, 11 January 1996, Bruyns 6607 (holotype BOL!, isotype MO!). Figs 4 , 5.

Bisexual spiny glabrous succulent 0.05–0.3 × 0.15–0.4 m with many branches from similar stem, stem with fibrous roots arising from it, densely branched at ground level and not rhizomatous. Branches erect, 20–170 × 7–10 mm, 4-angled, not constricted into segments, smooth, bright pea-green; tubercles in decussate pairs fused vertically into 4 low angles along branches with surface flat or slightly concave between angles, conical and truncate, projecting 2–4 mm from angles, with spine-shields 4–7 mm long, 1–2 × 2–3 mm above spines and 2–6(–8) mm long and more slender below spines but remaining well separated from next, bearing 2 spreading to slightly deflexed initially reddish brown (later dark brown) spines 6–10 mm long; leaf-rudiments on tips of new tubercles towards apex of branches, 0.8–1 × ± 0.5 mm, erect, fleeting, deltoid, sessile, with small stipular prickles 1–2 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 short peduncle 1–2 mm long and thick, with 2 ovate bracts ± 1 × 2 mm subtending lateral cyathia; cyathia shallowly cupular, glabrous, 4–5 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 ± 2 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.

Distribution & Habitat: — Euphorbia pisima is found to the north of the small town of Ohrigstad, between Abel Erasmus Pass and the village of Moremala, with another collection in Bewaarskloof in the Strydpoort Mountains, further to the north-west. Around Ohrigstad it occurs on stony dolomitic slopes with many other small succulents, small tufts of grass and a low-growing species of Xerophyta among scattered trees. Plants usually grow wedged into crevices between rocks. In the Strydpoort Mountains it grows on steep slopes in crevices in dolomitic rocks.

Discussion: — Euphorbia pisima grows into dense clumps of bright pea-green branches (from where the name is derived), in which the tubercles form four low angles along each branch. The colour of the branches and their continuous angles separate E. pisima from plants of E. clivicola occurring in the same area (where the branches are greyer and the tubercles are not fused into angles). In these features it is more similar to E. lydenburgensis in which, however, the branches are always 12–20 mm thick. The leaf-rudiments are particularly tiny, narrower than in E. lydenburgensis and smaller than those of E. clivicola .

Flowering in E. pisima usually takes place between late July and October. The bright yellow cyathia superficially resemble those of E. clivicola and E. schinzii but they differ in the longer peduncles of the lateral cyathia in each cyme, in the short, fused portion of the styles and in the longer pedicel of the female florets.

Additional specimens examined: — SOUTH AFRICA. Limpopo: Strydpoort Mtns, farm Royle, Bewaarskloof, along Mphogodima River (2429BB), 1000 m, Winter 5200 (BOL). Ohrigstad district, farm Branddraai (2430DA), Van der Merwe sub Division of Botany 3854/6/38 (PRE), Van der Merwe 1694 (K, PRE). Abel Erasmus Pass (2430DA), 1250 m, Bruyns 13559 (BOL). Moremala (2430DB), 1300–1700 m, Bruyns 7022 (BOL).

Figures

FIGURE 4. Euphorbia pisima. A, B, young spines and leaf-rudiment from above (scale 2 mm, as for B–E). C, side view of young spines and leaf-rudiment. D, side view of cyme in second male stage (females beginning to shrivel). E, side view of cyathium in female stage. F, anthers and bracteole (scale 1 mm, as for G, H). G, H, female floret. Drawn by P. Bruyns from Bruyns 6607.