3. Euploca ovalifolia (Forssk.) Diane & Hilger, Bot. Jahrb. Syst. 125(1): 48. 2003.

Fig. 2C-E

Heliotropium ovalifolium Forssk., Fl. Aegypt.-Arab.: 38. 1775. Type: Yemen, Al-Hadiyah [ Hadïe], Forsskål, 299 (holotype C [C10002362!], isotype BM [BM000795522!]).

Heliotropium coromandelianum J. Köenig ex Retz., Observ. Bot. 2: 9. 1781. Type: India, Köenig s.n. (holotype C [C10008743!]; isotype BM [BM000795508!]).

Heliotropium gracile R.Br., Prodr. Fl. Nov. Holland.: 493. 1810.

Heliotropium ovalifolium ver. Heliotropium gracile (R.Br.) Domin, Biblioth. Bot. 22(89): 546. 1928. Type: Australia, Northern Territory, North Island, 19 Dec 1802, Brown 2924 (lectotype, designated by Craven 1996, p. 559: BM [BM001040588!]; isolectotypes: K [K000998264!, K000998263!] GH [GH00097831]).

Type.

Based on Heliotropium ovalifolium Forssk.

Distribution.

Tropical Africa, Madagascar, Arabian Peninsula, Pakistan, India, Laos, Cambodia, Vietnam, Thailand (Fig. 1C), Australia, Solomon Islands.

Ecology.

Open area, sandy soil on riverbanks, rice fields, grassland, along roadsides; ca. 200 m alt., flowering and fruiting from December to May.

Specimens examined.

Thailand, Northern: Lamphun, Mae Ping NP, 22 May 2019, Thammarong et al. 673 (QBG); Tak, Tha Song Yang-Mae Sa Riang, Moei river, 22 Mar 2006, Pooma et al. 6220 (BKF, L); Bhumibol Dam, 200 m alt., 29 May 2008, Pooma et al. 7073 (BKF); Ban Maesong, 23 June 2005, Pooma et al. 5443 (BKF); Mae Sa Riang-Mae Sot road, 15 May 2007, Pooma et al. 6786 (BKF, E) .

Vernacular.

Nguang chang dok khao (งวงช้างดอกขาว).

Diagnostic characters.

Euploca ovalifolia is newly recorded for Thailand. It is recognised by elliptic to obovate or oblanceolate leaves with silky silver hairs, spike-like or scorpioid cymes inflorescence with pedicels up to 2 cm long and a white corolla with a yellowish to yellow centre. This species is similar to Heliotropium indicum in its inflorescence form, but differs in its leaf shape, bracteate inflorescences (vs. ebracteate in H. indicum) and fruit breaking up into four nutlets (vs. breaking up into two nutlets in H. indicum).