Euphorbia mongoliensis M. H. Li & C. H. Zhang, 2021

Zang, Er-Huan, Zhang, Ming-Xu, Wang, Wen-Le, Zhang, Chun-Hong & Li, Min-Hui, 2021, Euphorbia mongoliensis (Euphorbiaceae), a new species from Inner Mongolia, China, Phytotaxa 501 (1), pp. 151-161 : 155

Euphorbia mongoliensis M. H. Li & C. H. Zhang , sp. nov. ( Figs. 2–4 )

Diagnoses:— The new taxon is distinct from the known species of the genus Euphorbia in Inner Mongolia. It is similar to E. esula and E. caesia in many morphological characters. It is distinguished by a stem height of 2–10(–12) cm, usually less than 10 cm (vs. longer stems of more than 30 cm in E. esula , 10–30(–50) cm in E. caesia ); leaves being auriculate at the base, the margins entire and slightly recurved, both sides slightly white farinose (vs. wedged, round or truncate in E. esula and E. caesia , not recurved in both). The capsule surface is tuberculate (vs. not tuberculate in E. esula , glabrous or finely rugose in E. caesia ) ( Table 2).

Type: — CHINA. Inner Mongolia: Ordos City, Dongsheng District, Jilao Qingchuan Wetland Park , 1431m, 39°48’52.47”N, 109°53’33.57”E. 20 May, 2020, M. H . Li & C. H . Zhang 150602200520001 LY (holotype PE!; isotype HIMC!) .

Description: —Herbaceous, perennial. Roots cylindrical, branched or not, brown, 20–55 cm × 1.5–3 mm. Stem erect, single or basally branched, 2–10(–12) cm tall, usually less than 10 cm, 1.2–3 mm in diameter, with or without shallow edges, slightly white farinose, puberulent. Leaves oval triangular or oval lanceolate, 1.2–1.5 × 0.2–0.5 cm; apex acuminate or slightly blunt, base gradually wider and auriculate; the margins entire and slightly recurved, both sides slightly white farinose, sessile; midvein prominent. Ray-leaves 6–10, oval triangular or oval lanceolate, 0.4–0.7 × 0.2–0.4 cm, apex blunt or acuminate, slightly auriculate and sessile at the base, semiamplexicaul; 6–10 terminal rays (sometimes have axillary rays), with the same number of ray leaves, from the base of the ray leaves, 0.5–1.5 cm. The apex of each terminal ray often has 1–2 dichasia. The inflorescence is solitary at the apex of a dichasium, and the base is sessile. The base of terminal rays have one pair of subcyathial raylet leaves, triangular broadly ovate, 0.3–0.55 × 0.35–0.65 cm, apex shortly acuminate to rounded, and the base is truncated; cyathium campanulate, 2–3 × 1.5–2.5 mm, smooth, glabrous, 5-lobed on the margin, lobes rounded to oval triangular, tomentose on margin and inside; cyathial glands 4, semicircular, transversely ellipse, reniform or crescent shaped, with or without horns at both ends, yellow brown or dark brown; 2–3 stamens and the ovary stalk exserted from cyathium, ovary ovoid, trilocular, styles 3, completely separate, stigma apex 2-deep lobed. Capsule trigonous globose, 2.5–3.5 × 3.0–4.0 mm, with 3 vertical furrows, glabrous, tuberculate, with a stalk, 1.5 mm long; styles persistent. Seeds ovoid-globose, 2.0–2.5 × 1.0– 1.5 mm, yellow-brown; caruncle present, peltate, sessile.

Phenology: —Flowering and fruiting from May to June.

Distribution and habitat: —Occurs on dry hillsides. It is distributed in Dongsheng District and Kangbashi District, Ordos City, Inner Mongolia. The type was collected from Dongsheng District.

Etymology:—The epithet refers to the area of its occurrence (Inner Mongolia).

Figures

FIGURE 2. Morphology of E. mongoliensis (A. whole plant; B. individual plants, habit in the field). Photos: C. H. Zhang. Based on M. H. Li & C. H. Zhang 150602200520001LY (PE).

FIGURE 3. Details of morphology of E. mongoliensis. A. upper view of subcyathial raylet leaves; B. reverse side of subcyathial raylet leaves; C. mature fruits; D. cross section of fruits; E. top view of inflorescence; F. lateral view of inflorescence; G. detail of leaves and stem; H. seeds. Photos: C. H. Zhang and M. X. Zhang. Based on M. H. Li & C. H. Zhang 150602200520001LY (PE).

FIGURE 4. Illustrations of E. mongoliensis. A. plant aerial parts; B. cyathium; C. fruits; D. transverse section of fruits; E. seeds; F. roots. Illustrated by W.Y. Li based on M. H. Li & C. H. Zhang 150602200520001LY (PE).