Heliotropium L., Sp. Pl.: 130. 1753.

Rueangsawang, Kanokorn & Chantaranothai, Pranom, 2023, A taxonomic synopsis of Heliotropiaceae and new combinations in Heliotropium from Thailand, PhytoKeys 232, pp. 189-210 : 189

Heliotropium L., Sp. Pl.: 130. 1753.

Tournefortia L., Sp. Pl.: 140. 1753. Type species. Tournefortia hirsutissima L. [= Heliotropium verdcourtii Craven].

Argusia Boehm. in Ludwig, Def. Gen., ed. Boehmer: 507. 1760. Type species: Argusia sibirica (L.) Dandy.

Messerschmidia L. ex Hebenstr., Nov. Comm. Acad. Sci. Imp. Petrop. 8: 315, t. 11. 1763. Type species: Tournefortia sibirica L.

Tetrandra (DC.) Miq., Fl. Ind. Bat. 2: 928. 1858. Type species: Tetrandra wallichii Miq. [= Tournefortia tetrandra Blume].

Mallotonia (Griseb.) Britt., Ann. Missouri Bot. Gard. 2: 47. 1915. Type species: Mallotonia gnaphalodes (L.) Britton.

Type species.

Heliotropium europaeum L.

Description.

Annual herbs, climbing shrubs or small trees. Leaves petiole; lamina ovate, elliptic to obovate or elliptic to lanceolate, apex acute to acuminate, obtuse or rounded, margin entire or irregularly undulate, strigose, stiff hairs or greyish-white tomentose on both surfaces. Inflorescences terminal or axillary, scorpioid cymes, subcorymbose or dichotomously branched, dense 2-rowed scorpioid cymes, ebracteate. Flowers 4-5-merous. Calyx 5-lobed, lobes lanceolate to ovate. Corolla pale green, white to pinkish-white, greenish to yellowish, with a yellow-orange throat inside, funnel-shaped or tube cylindrical, lobes broadly ovate to orbicular, throat glabrous inside. Stamens included, sessile or with short filaments; anthers ovate-lanceolate or elliptic-oblong. Ovary entire. Fruits drupe, deeply bilobed or distinctly lobed, mesocarp thinly fleshy or juicy, endocarp dividing into two 2-seeded nutlets.