4. Lobelia hainanensis F. E. Wimmer, Ann. Naturhist. Mus. Wien. 56: 348. 1948.
海南半边莲 hai nan ban bian lian
Stems 4-angular, ascending or erect, up to 20 cm tall, glabrous. Leaves alternate, denser at upper part of stems, subsessile; blade oblong or elliptic, ca. 15 × 7 mm, glabrous, base cuneate, margin cartilaginous-crenulate, apex obtuse. Flowers solitary, axillary at leaves; pedicels ca. 12 mm, glabrous, ± as long as leaves. Hypanthium broadly top-shaped, ca. 2 × 2 mm; calyx lobes sublinear, ca. 3 mm, glabrous, margin entire, apex acute. Corolla 2-lipped, blue, ca. 1 cm, glabrous; upper lobes spatulate, shorter than lower ones; lower lobes obovate, ca. 4 × 2 mm, base with a pale black spot, apex rounded, mucronate. Filament tube ca. 5 mm, glabrous; anther tube gray-brown and black striate, ca. 2 mm, back puberulent at apex; lower 2 anthers barbate at top.
No specimens have been examined by us, but based on the original description, we judge it to be distinct from its allies.