Hydrocotyle chiangdaoensis Murata

Wen, Jun, Zhu, Jun-Wen, Zhu, Ren-Bin & Song, Chun-Feng, 2025, Taxonomic studies on the genus Hydrocotyle (Apiales) from China: The distribution and morphology of H. chiangdaoensis, with H. calcicola reduced to a synonym, PhytoKeys 255, pp. 247-260 : 247-260

Hydrocotyle chiangdaoensis Murata , Acta Phytotax. Geobot. 25: 97. 1973.

= Hydrocotyle calcicola Y. H. Li , Guihaia 9: 25. 1989. = Hydrocotyle sibthorpioides var. calcicola (Y. H. Li) S. L. Liou , Fl. Yunnanica 7: 363. 1997. Type: China. Yunnan, Jinghong City, Jinuo Mountain, 11 August 1975, G. D. Tao 13671 (holotype: HITBC 0037397 ; isotype: KUN 0467704 ).

Type.

Thailand. Northern Chiang Mai, 26 September 1971, Murata G. et al. T- 15040 (holotype: KYO 00028951 ; isotype: KYO 00028952 , L 0008361 ; TI 00083127 ; AAU). Figs 1 A , 2 .

Etymology.

This species is currently found only in limestone areas, so we have retained the Chinese name 石山天胡荽 [Pinyin: shí shān tiān hú suī] of Hydrocotyle calcicola .

Description.

Herbs, 15–60 cm tall, glabrous. Stems erect or ascending, slender, branched, with ascending branches 2–20 cm long, rooting only at nodes of the basal stem and never elsewhere. Membranous leaves subrounded or cordate, gradually smaller above, palmately 5–9 - lobed, lobes usually crenate at the margin, conspicuously covered with sparse spiny hairs above towards the veins, glabrous beneath, 0.5–4.5 cm long, 0.7–4 cm wide. Petiole 0.7–3.5 (5) cm long, glabrous. Stipules membranous flabellate-orbiculate, 1–5 mm wide, palmate-dissected or irregularly. Terminal umbels cymose, umbels 2–3, and usually solitary at the other nodes; slender peduncles not quite equaling, 0.5–10 mm long; umbel 2–5 - flowered, sessile; bracts ovate-lanceolate, about 1 mm long; petals ovate-lanceolate, about 0.5 mm long, white, 4 or 5; membranous filaments equal to or slightly shorter than the petals; anthers ovate; style about 0.2 mm long. Mericarps broadly ovate or subcordate, 1–1.3 mm long, 0.8–1.2 mm wide, with papillose setae in the furrow or sometimes smooth on the outside, ribs conspicuously convex. The mericarps are not easy to separate when mature.

Distribution.

China (Yunnan: Jinghong, Lincang, Pu’er), Myanmar (Southern Shan State: Ywangan Township), and Thailand (Chiang Mai).

Habitat.

The species grows on limestone at elevations of 1300–2175 m above sea level, always in dense evergreen forests, shady and moist places.

Phenology.

Flowering and fruiting from July to November.

Additional specimens examined.

China. Yunnan Province • Jinghong City, Jinuo Mountain , 21°59'N, 101°05'E, alt. 1490 m, 11 August 1975, G. D. Tao 13671 ( HITBC 081533 , KUN 0467704 ) • Lincang City , Yongde County, 24°09'27.3"N, 99°14'58"E, alt. 1923 m, October 2015, LiYL 1395 ( KUN 1372015 ) • Pu’er City , Lancang County, 26 September 1993, Y. Y. Qian 3024 ( HITBC 0122528 ) • Pu’er City , Ning’er County, 23°04'12.74"N, 101°01'43.3"E, alt. 1733–1840 m, 23 August 2023, WJ 2361 ( NAS 00714697 – NAS 00714702 ) • Pu’er City , Ning’er County, 23°04'22.6"N, 101°01'37.7"E, alt. 1798 m, 28 September 2020, D. P. Ye 1994 ( HITBC 0063922 , PE 02521420 ) • Pu’er City , Ximeng County to Lancang County, 22°45'N, 99°40'E, alt. 1900 m, 24 October 1989, G. D. Tao et al. 39828 ( HITBC 0122527 , KUN 0462683 ) .

Myanmar. Southern Shan State • Ywangan Township , 21°13'50.2"N, 96°31'03.7"E, alt. 1372 m, 6 October 2017, Kim et al. MM- 6405 ( HHU) .

Thailand. Chiang Mai • Doi Chiang Dao , alt. 1300–1900 m, 27 September 1971, G. Murata et al. T- 15147 ( K 005513596 , L. 2583778 , P 03259185 ) • Doi Chiang Dao , alt. 1900–2175 m, 14 September 1967, T. Shimizu et al. T- 10125 ( K 005513595 , L. 2583136 ) • Doi Chiang Dao , alt. 2000 m, 16 July 1958, Th. Sørensen et al. 4172 • Doi Chiang Dao , alt. ca. 1700 m, 3 November 1922, A. F. G. Kerr 6530 ( K 005513556 ) • Doi Chiang Dao , 18 October 1926, no. 412 ( K 005513592 ) • Doi Chiang Dao , alt. 1400–1800 m, 5 January 1966, M. Tagawa & K. Iwatsuki T- 4389 ( L. 2583137 ) • Doi Chiang Dao , alt. 1975 m, 10 November 1995, J. F. Maxwell 95-1157 (Topotype, L. 4214318 ) .

Note.

Hydrocotyle chiangdaoensis has been recorded in China, Myanmar, and Thailand. This species is well characterized by its palmate-dissected or irregular stipules, cymose terminal umbels, and papillose-setulous fruits. This species is restricted to limestone areas. Hydrocotyle chiangdaoensis differs from H. sibthorpioides typically by its roots only growing at nodes of the basal stem and never elsewhere, with terminal cymose umbels and papillose-setulous fruits.

Figures

Figure 1. Holotype sheets of Hydrocotyle chiangdaoensis (A) and H. calcicola (B). The arrows indicate the roots of the species.

Figure 2. Isotype sheets of Hydrocotyle chiangdaoensis. The arrows indicate the roots of the species.