Christolea pterosperma Al-Shehbaz

Al-Shehba, Ihsan A., 2022, Christolea pterosperma (Brassicaceae), a new species from Tibet (China), Phytotaxa 555 (2), pp. 205-208 : 205-208

Christolea pterosperma Al-Shehbaz , sp. nov.

Diagnosis:— Christolea pterosperma differs from its congener by having entire leaves and winged seeds.

Type:—[ CHINA. W Tibet (Xizang)], “in lipidosis schistosis siccis mobilibus, ad Houkio-ghauti Kunaures, V. Jacquemont 1863” (holotype, P; isotype, P). Figures 1 , 2 .

Description:— Herbs perennial, puberulent on leaves and stems; caudex slender, surculose, loose, not covered with leaf remains of previous seasons, with branches 1–3 mm wide and some exceeding 15 cm long, Trichomes simple, straight or slightly crisped, 0.05–0.25 mm long. Stems 2–4 cm tall, few branched, herbaceous, glabrous proximally, puberulent distally. Leaves cauline, fleshy, 3–5 per branch; petiole 1–5 mm long; leaf blade suborbicular to broadly obovate, 7–15 × 3–10 mm, sparsely to moderately puberulent, entire, rounded at apex, cuneate to base. Racemes ebracteate, 10–25-flowered, slightly elongated in fruit; fruiting pedicels 4–7 mm long, sparsely to moderately puberulent, horizontal to divaricate, straight or slightly arcuate-curved. Normal flowers not seen. Fruit narrowly oblong, 6–10 × 2–2.2 mm, suberect, not appressed to rachis, straight, strongly latiseptate, with 4–6 seeds and/or aborted ovules; valves smooth, sparsely puberulent with minute straight trichomes to subglabrous, apex acute, base obtuse; style 0.3–0.6 mm long, conical; stigma entire. Seeds brown, orbicular to suborbicular, 2–2.2 × 1.7–2.2 mm, strongly flattened, broadly winged all around; wing 0.25–0.35 mm wide; cotyledons accumbent.

Habitat: —Dry, loose, stony or rocky schist.

Distribution: —Endemic to China and known thus fare only from the type collection above.

Discussion: — Christolea pterosperma resembles both C. crassifolia and C. niyaensis in having thick, subfleshy, petiolate cauline leaves and latiseptate siliques. However, it can be easily distinguished from both by having winged (vs. wingless) seeds, accumbent (vs. incumbent cotyledons), entire (vs. dentate or rarely laciniate) cauline leaves, 4–6 (vs. 10–20) ovules per ovary, and smaller fruits 6–10 × 2–2.2 mm (vs. 10–30(–35) × (2–)2.7–4(–4.5) mm). As C. crassifolia , it is long-lived perennial that differs by the long, slender, surculose caudex instead of short, woody, non-surculose caudex. Christolea niyaensis is short-lived perennial with slender, short caudex. The type collection was on a loan since 1998 and, therefore, no images were taken then.

According to Stafleu & Cowan (1979: 403), Victor Jacquemont conducted his fieldwork in the Himalayas in 1829 into 1832, the year he died. Although his collections were numbered, no dates were given. The lectotype of Christolea crassifolia was anonymously annotated as collected between 15 and 22 August 1831. Because C. pterosperma was gathered from the same general area, it was probably collected around that time.

Christolea niyaensis a narrow endemic known for a single collection [ China, Xinjiang, Minfeng (Niya) Xian, Kunlun Shan, 2700 m, 14 June 1982, Qi Quei 55 (holotype, XJA!)], whereas C. crassifolia is widespread and distributed in Afghanistan, China (Qinghai, Sichuan, Xinjiang, Xizang), India, Nepal, Pakistan, and Tajikistan. The type collection of the latter, Jacquemont 1837, is represented by three sheets, and the name has not yet been lectotypified. Jafri (1973: 156) listed the type as “K, P”, whereas Al-Shehbaz (2015) listed the holotype at P and possible isotypes at K and P. The name is formally lectotypified herein:

Christolea crassifolia Cambess. in Jacquemont, Voy. Inde 4: 17. 1844. Type indication:— CHINA, Tibet, “ad jugum vulgò Houkio-ghauti ad fines provinciae Kanaor et Tartaria sinensis,” [15–22 Aug. 1831], V. Jacquemont 1837 (lectotype here designated: P-01817644!; isolectotypes: K-000247270!, P-01817645!).

Figures

FIGURE 1. Image of holotype of Christolea pterosperma.

FIGURE 2. Christolea pterosperma. A. Plant showing surculose caudex. B. Fruiting branch. C. Fruit. D. Seed. Drawn by I. Al-Shehbaz from the holotype (Jacquemont 1863, P).