The new species is most similar to O. alatiflora, but can be distinguished from the latter by the inflorescences which are erect from the earliest developmental stages (vs. drooping when young, then erect), the small and equally-sized calyx lobes 0.5–0.7 mm long (vs. 0.9–1.8, sometimes to 2.5 mm long and usually unequal), the longitudinal wings on the corolla tube which run to the middle of the tube and are straight (vs. wings running along entire length and obviously undulate) and the strongly reflexed corolla lobes (vs. spreading) at anthesis.

Figure 1. 

Ophiorrhiza revoluta A flowering branch B stipule C part of inflorescence D longitudinally dissected short-styled flower E longitudinally dissected long-styled flower F capsules. Drawn from the holotype by X.Y. Zeng.

China. Guangxi Zhuang Autonomous Region: Napo County, Pingmeng Town, Guijiao Village, growing in limestone areas, under evergreen broad-leaved forests, rare, 23°0′30"N, 105°51′53"E, 1080 m alt., 25 Oct 2013 (fl.), L. Wu, C. Du & S.S. Mo 4031 (holotype: CSFI 080032!; isotypes: BNU! CSFI! IBK!).

Figure 2. 

Ophiorrhiza reflexa A, B habit C stipule D young inflorescence E inflorescence in lateral view F inflorescences in different development stages G bracts from lower part to upper part of inflorescence H leaves I corollas in lateral view J corollas in top view K longitudinally dissected long-styled flower L longitudinally dissected short-styled flower M infructescence. Photos by L. Wu. Scale bars: 3 mm (C); 1 cm (G, J–L); 2 cm (E, F, I, M); 10 cm (H).

Perennial herbs or subshrubs, suberect, up to 100 cm tall. Stems terete to slightly compressed, glabrous. Leaves in subequal pairs; petiole 4–6 cm long, smooth; blade thickly papery, adaxially green, abaxially pale green, broadly ovate to elliptic-ovate, 11–17 × 5–8 cm, glabrous on both surfaces, base broadly cuneate to obtuse, apex acuminate or subacute, margin entire; lateral veins 9–11 on each side of the mid-rib; stipules caducous, triangular ovate, ca. 1.5 mm long, apex obtuse. Cymes terminal, erect from youngest developmental stages, many-flowered; peduncle stout, 3–6 cm long, puberulent; bracts linear-lanceolate, 8–19 × 1–3 mm, glabrous on both surfaces, apex acute; pedicels 1–3 mm long, puberulent. Flowers heterostylous. Calyx densely pilosulous to puberulent; hypanthium turbinate, 5-ribbed; lobes 5, equal, 0.5–0.7 mm long, triangular, subglabrous abaxially, with a gland in each sinus. Corolla white or sometimes slightly pink at apex, tubular-funnelform, outside glabrous; tube 1.3–1.5 cm long, outside longitudinally winged from apex to middle, wings straight, ca. 0.8 mm wide; lobes 5, ovate-triangular, ca. 4 × 3 mm, reflexed, inside densely pubescent, apex acute. Stamens 5; anthers linear, 2.5–3 mm long. Stigma bilobed; ovary 2-celled. Long-styled flowers: inside with a ring of white hairs at the middle of the corolla tube and puberulent from the middle up to the throat; stamens included, positioned near the middle of the corolla tube; style densely pubescent; stigma positioned near corolla throat, lobes ovate-elliptic, ca. 1.4 mm long. Short-styled flowers: sparsely pubescent at the middle of the corolla tube; stamens reaching slightly beyond corolla throat, not exserted; style included near the middle of the corolla tube, glabrous; stigma lobes lanceolate-elliptic, 2–3 mm long. Capsules rhomboid, ca. 4 × 9 mm, glabrous.

Figure 3. 

Morphological comparison of Ophiorrhiza alatiflora and O. japonica A–H O. alatiflora A habit B inflorescences in different developmental stages C calyces and corollas in lateral view D corollas in top view E inflorescence F young inflorescence G longitudinally dissected long-styled flower H longitudinally dissected short-styled flower I–M O. japonica I habit J corollas in lateral view K corollas in top view L, M young inflorescence. Photos by L. Wu. Scale bars: 1 cm (C–H, J–M); 2 cm (B).

Flowering from October to January; fruiting from March to June.

Ophiorrhiza reflexa grows in moist places under evergreen broad-leaved forests in the limestone region of Napo County, Guangxi, China (Fig. 4).

Figure 4. 

Geographical distribution of Ophiorrhiza reflexa (red triangle, Napo County) and O. alatiflora (blac triangle, Malipo County).

Three populations of Ophiorrhiza reflexa with more than 1000 individuals at each site have been found during our field investigations. The three sites all belong to Laohutiao Provincial Nature Reserve, which is well-protected and not under threat (Tang et al. 2013). All individuals are distributed in an area of ca. 50 km² (10 × 5 km) and have remained roughly stable for the past 10 years. According to currently available data, O. reflexa is preliminarily assessed as Least Concern (LC) according to IUCN Categories and Criteria (IUCN 2023).

(paratypes). China. Guangxi Zhuang Autonomous Region: Napo County, Baisheng Town, Nongming Village, 1200 m alt., 14 May 2013 (fr.), L. Wu 3706 (BNU! CSFI!); same locality as holotype, 25 Oct 2013 (fl.), L. Wu, C. Du, S.S. Mo 4033 (BNU! CSFI! IBK!); Napo County, Pingmeng Town, Guigan Village, under evergreen broad-leaved forests, 1100 m alt., 7 Jan 2014 (fl.), L. Wu 4173 (BNU! CSFI!); ibid., 10 May 2017 (fr.), L. Wu & Z.J. Wen 5891 (CSFI!).

The species epithet refers to the reflexed corolla lobes. The Chinese name is given as ‘fan-ban-she-gen-cao (反瓣蛇根草)’.

Ophiorrhiza is a taxonomically difficult genus despite its easy distinction at genus level by the unique fruits. Misidentification or synonymy have become a major problem (Schanzer 2004; Wu et al. 2017c). As mentioned above, the reason is mainly the high morphological variation and insufficient knowledge of important characters, especially flowers (e.g. Ophiorrhiza nigricans H.S.Lo was synonymised as O. japonica Blume by Duan and Lin (2007); O. pseudonapoensis L.Wu & Q.R.Liu has been misidentified as O. napoensis H.S.Lo until Liu et al. (2023)).

Based on our field investigations of Ophiorrhiza in China and careful studies of relevant literature and specimens, about 88% of the known species are confirmed to be distylous plants. At least 52 species have been observed by us with both long- and short-styled flowers in the same population. Meanwhile, we found that the growth pattern of the inflorescence is relatively stable in Chinese Ophiorrhiza species. Nearly half of the Chinese Ophiorrhiza species have inflorescences that are erect from the youngest developmental stages (see Fig. 2D, F), whereas the other half have inflorescences drooping when young, then gradually becoming erect (see Fig. 3B, F). In the study of Ophiorhiza species from the Pacific Islands, Darwin (1976) made similar observations and pointed out that the morphology of the inflorescence was taxonomically useful. However, until now, inflorescences have not received sufficient attention in most of the past studies (Lo 1990, 1999; Deb and Mondal 1997; Chen and Taylor 2011).

Ophiorrhiza reflexa is most similar to O. alatiflora, both of them growing in limestone hills under dense monsoon forests. However, the former differs from the latter mainly by its erect (vs. drooping when young, then erect) inflorescences (Figs 2D, F, 3B, F), 0.5–0.7 mm long and equal calyx lobes (vs. 0.9–1.8, sometimes to 2.5 mm long and unequal, sometimes distinctly, calyx lobes; Figs 2E, K, L, 3C, G, H), strongly reflexed (vs. spreading) corolla lobes at anthesis (Figs 2E, F, K, L, 3C–E, G, H) and corolla outside with straight (vs. obviously undulate) wings from top to middle (vs. along entire length) (Figs 2E, L, 3C, G). Additionally, Ophiorrhiza reflexa is morphologically similar to O. japonica Blume, the most widely distributed Ophiorrhiza species in China. Both of them have caducous stipules, linear-lanceolate bracts, heterostylous flowers and tubular corollas with a villous ring positioned near the middle of the corolla tube in long-styled flowers. However, the new species differs from O. japonica by the erect (vs. drooping when young, then erect) and lax (vs. congested or somewhat lax) inflorescences (Figs 2D, F, 3I, L, M), the strongly reflexed (vs. spreading) corolla lobes at anthesis (Figs 2E, I–F, 3I–K) and the longitudinally winged corolla with ca. 0.8 (vs. ca. 0.5) mm wide wings (Figs 2L, 3J). Further distinctive characteristics of the three species are shown in Table 1.