Description from Flora of China
Pteracanthus forrestii (Diels) H. P. Tsui; P. rotundifolius (Benoist) Bremekamp; Strobilanthes panpienkaiensis H. Léveillé; S. rotundifolia Benoist.
Herbs to 30-75 cm tall, isophyllous. Stems 4-angled, thinly pilose with gland-tipped trichomes, glabrescent, basally woody. Leaves subsessile; leaf blade ovate to rarely ovate-oblong, 2-5 × 1.2-3 cm, both surfaces thinly pilose, adaxially with cystoliths, secondary veins ca. 4 on each side of midvein, base rounded, cordate, or rarely cuneate, margin crenate to subentire, apex acute to obtuse. Inflorescences terminal or very rarely also from apical leaf axils, spikes, 5-15 cm; rachis pilose with gland-tipped trichomes; bracts leaflike, pilose with gland-tipped trichomes; basal bracts ovate-elliptic, 1-3 × 1-2 cm, margin obscurely crenate; apical bracts lanceolate, 7-10 × ca. 3 mm, margin entire; bracteoles linear to narrowly oblong, 6-11 × ca. 1 mm, pilose with gland-tipped trichomes. Flowers 1-2.5 cm apart on rachis. Calyx 0.8-1.2 cm, 5-lobed almost to base; lobes linear with one ca. 2 mm longer than others, pilose with gland-tipped trichomes. Corolla blue to purple, 3.2-4 cm, curved, outside with a few trichomes, inside glabrous except for trichomes retaining style; tube basally cylindric and ca. 2 mm wide for ca. 5 mm then bent to ca. 90° and widened to ca. 1.5 cm at mouth; lobes ovate, ca. 6 × 7 mm, apex obtuse. Stamens 4, included; shorter filament pair ca. 2 mm; longer filament pair ca. 8 mm, shortly pubescent; anther thecae oblong, ca. 2 × 0.8 mm; pollen type 3. Ovary gland-tipped puberulent at tip; style ca. 2.8 cm. Capsule oblong, ca. 1.2 cm, apically gland-tipped pilose, 4-seeded. Seeds dark brown, ovate in outline, ca. 3 mm, pubescent; areola white, small. Fl. Jul-Aug.
Strobilanthes forrestii was misidentified as S. extensa (Pteracanthus extensus) by Handel-Mazzetti (Symb. Sin. 7: 895. 1936), C. Y. Wu (Index Fl. Yunnan. 2: 1682. 1984), and H. P. Tsui and C. C. Hu (FRPS 70: 136. 2002; Fl. Yunnan. 16: 696. 2006).
● Forests, grass slopes; ca. 3000 m. Yunnan.