Ophiorrhiza xishuiensis Sheng H. Tang, Jia W. Yang & X. Z. He sp. nov.

Figs 1, 2, 3

Diagnosis.

The new species is most similar to O. japonica, O. guizhouensis, and O. chinensis by the length of the stipules, calyx lobes and corolla tube, the shape of the corolla, and the distribution areas and altitudes. It differs from O. japonica and O. guizhouensis by the 1–7 cm long rooting stems (vs. 10–30 cm, or longer), the fact that most leaves are arranged in markedly unequal (vs. subequal) pairs, the style reaching above (vs. below) the middle of the tube in the short-styled flowers, and the glabrous (vs. pubescent) style in the long-styled flowers. It is distinct from O. chinensis by the congested-cymose (vs. paniculiform to cymose) inflorescences, the well-developed and persistent (vs. absent or reduced and caducous) bracteoles, and the glabrous (vs. pubescent) style in the long-styled flowers.

Type.

China • Guizhou Province: Xishui County, Sanchahe Town, Guizhou Xishui National Nature Reserve, 28°33'17"N, 106°23'49"E, 1129 m, 13 March 2025, Sheng H. Tang & Xuan-Ze He 202503002 (holotype: CSH! [Barcode: CSH 0221076]; isotypes: CSH!, the Guizhou Botanical Garden!).

Description.

Perennial herbs, erect, 10–20 cm tall; stems glabrous, terete, 2.5–4.5 mm in diameter, 3–11 nodes, most internodes ascending and most nodes not rooting, rooting stem 1–7 cm long, creeping, a very small amount of white sap present when petiole is cut. Leaves mostly in markedly unequal pairs; petiole 0.5–4.5 cm long, glabrous, terete, 1–2 mm in diameter; blade drying papery, grayish green adaxially, pale green abaxially, oblanceolate, elliptic, lanceolate-elliptic, or oblong, larger ones 6–17 × 1.8–5 cm, smaller ones 1.5–5 × 0.5–1.5 cm, both surfaces glabrous or sometimes hirtellous adaxially, base cuneate, somewhat inequilateral, rarely subequilateral, margins entire, apex acute; secondary veins 6–9 pairs; stipules triangular, 0.8–1.2 mm long, caducous, with 5–6 globose colleters at the inner base. Inflorescences terminal, congested-cymose, 6–36 flowers per cyme, drooping at the early stage, then erect; peduncle 5–8 cm long, rarely shorter, 1.3–2.5 mm in diameter, glabrous; axes 5–10 mm long, congested-cymose, densely puberulent on the inside; bracts usually absent and sometimes well-developed, a little larger than bracteoles, bracteoles persistent, ovate, broadly ovate, or oblong, 4.7–12 × 2.2–6.5 mm, glabrous, margins entire with sparse colleters sometimes, apex obtuse, sometimes acute, midrib prominent on both sides, sparse colleters adaxially and abaxially sometimes, with 1 globose colleter at each side of inner base. Pedicels puberulent, 1–2 mm long or flowers subsessile. Flowers distylous. Hypanthium oblate, compressed, 1–1.4 × 2.4–2.8 mm, 5 - ribbed, densely puberulent; calyx lobes 5, ovate, 0.5–1 × 0.5–0.7 mm, glabrous or sparsely puberulent outside, dorsally thickened, apex obtuse, with 1 globose colleter at each side of base outside and 1 globose colleter in each sinus. Corolla white or pale purplish red, drying pale yellow, tubular-funnelform, outside glabrous and longitudinally 5 - ridged from apex to base; tube 9–16 mm long; lobes 5, triangular-ovate, 5–7 × 3.8–4.5 mm, adaxially scaly hairy and scaly glandular-hairy, apex acute, slightly incurved with a very short rostrum. Stamens 5, anthers linear, 2–2.3 mm long. Ovary 2 - celled, densely puberulent to subglabrous. Long-styled flowers: corolla pubescent from below the middle up to the throat inside, without or with a white villous ring near middle of the tube; stamens inserted near the middle of the tube, filaments 0.3–0.4 mm long; style 9–12.6 mm long, glabrous, stigma positioned at the level of the throat or slightly exserted from the throat, lobes obovate or linear, 1.7–2.8 mm long. Short-styled flowers: corolla pubescent from below the middle up to the throat inside, without a white villous ring near the middle of the tube; stamens inserted in the throat, included or slightly exserted, filaments 1–1.2 mm long; style 4.5–7.5 mm long, reaching above the middle of the tube, glabrous, stigma positioned just below the throat, lobes linear, 3.2–3.4 mm long. Infructescence axes 8–16 mm long, densely puberulent on the inside. Capsules inverted triangle or submitriform, 4.7–5.7 × 7.8–10 mm, densely puberulent to subglabrous. Seeds numerous, rhomboid or nearly square, angled, 0.4–0.5 × 0.4–0.5 mm.

Phenology.

Flowering occurs from February to March, and fruiting occurs from April to July.

Etymology.

The new taxon was named after its type locality, Xishui County, Guizhou Province, China.

Vernacular name.

The Chinese name is “ Xí Shuǐ Shé Gēn Cǎo ” (习水蛇根草).

Distribution and habitat.

The species has been discovered in Guizhou Province (Xishui County, Chishui City), Sichuan Province (Xuyong County, Gulin County, Changning County, Weiyuan County, and Xuzhou District), and Chongqing City (Jiangjin District), China (Fig. 4). It grows in the Danxia landform, and thrives on moist, shady cliffs and sandy conglomerate surfaces. The Danxia landform is a red-bed landform characterized by steep cliffs.

Conservation status.

The species has been discovered in several counties and districts in Guizhou, Sichuan, and Chongqing, China. It is highly probable that additional populations exist in this region. Until further investigation is carried out, the species should be classified as “Data Deficient” (DD) following IUCN standards (IUCN 2024).

Additional specimens examined.

China • Sichuan Province: Gulin County, Huangjinglaolin Nature Reserve, 10 September 2013, Yi-Hua Tong et al. 13091025 (BNU barcode BNU 0018143 [photo!]); • Weiyuan County, Changtiankan, Guipiwan, Weiyuan team 4029 (SM barcode SM 718501570 & SM 718501571 [photo!]); • Xuyong County, Shuiwei Town, Guangmu Village & Xixi Village, 1,000 m, 16 April 2014, Lei Wu 4533 (BNU barcode BNU 0018141 & BNU 0018142 [photo!]); • Xuyong County, Shuiwei Town, during the journey from Guangmu Village (Group 2) to Suoluogou, 28°15'46"N, 105°31'0"E, 910 m, 13 June 2013, Xin-Fen Gao, Zhang-Ming Zhu & Wen-Bin Ju HGX 12115 (CDBI barcode CDBI 0226195 [photo!]); • Xuyong County, Shuiwei Town, Guandou Village, 28°14'16"N, 105°38'11"E, 850 m, 7 June 2013, Xin-Fen Gao, Yun-Dong Gao & Wen-Bin Ju HGX 11695 (CDBI barcode CDBI 0226617 [photo!]); • Xuyong County, Shuiwei Town, Guangmu Village, 28°09'37"N, 105°18'56"E, 1030 m, 20 February 2014, Wen-Bin Ju HGX 14071 (CDBI barcode CDBI 0227705 & CDBI 0227706 [photo!]); • Xuyong County, Longfeng Town, Siping Village, 28°09'02"N, 105°16'57"E, 960 m, 22 February 2014, Wen-Bin Ju HGX 14135 (CDBI barcode CDBI 0226957 & CDBI 0226958 [photo!]); • Changning County, Wanling Town (Wanling Commune), 600 m, 22 June 1977, s. coll. 0479 (SM barcode SM 718501565 [photo!]); • Xuzhou District, Longchi Town (Guangming Commune), Honghua Village, 500 m, 16 July 1977, Yibin team 539 (SM barcode SM 718501573 & SM 718501574 [photo!]); • Guizhou Province: Chishui City, Baoyuan Town, Lianhua Village, 28°20'34"N, 105°39'46"E, 448 m, 14 March 2025, Sheng H. Tang & Da-Zhu Tang 202503005 (the Guizhou Botanical Garden!).

Additional photographs examined.

China. Chongqing City: Jiangjin District, Simianshan Scenic Area, Xiang Liu (PPBC ID 21102971); Yong-Sheng Wei (PPBC ID 20813977, 20813979, 20813983, 20830320, 20830324, 20830330, 20830335, 20830339, 20830343, 20830353, 20848643, 20848645, 20848647, 20848649, 20848651, 20848655, 20848658).

Notes.

The new species is most similar to Ophiorrhiza japonica (Fig. 5), O. guizhouensis (Fig. 5), and O. chinensis (Fig. 5) by the length of stipules, calyx lobes and corolla tube, the shape of the corolla, and the distribution areas and altitudes. The new taxon is also similar to O. umbricola W. W. Sm., O. grandibracteolata F. C. How ex H. S. Lo and O. liuyanii L. Wu, Y. H. Tan & K. S. Nguyen by the congested-cymose inflorescences and well-developed bracteoles. It differs from O. umbricola by the 1–7 cm long rooting stems (vs. usually 15 cm, or longer), the somewhat inequilateral, rarely subequilateral leaf blade bases (vs. subequilateral), the 5–8 cm long (rarely shorter) peduncle (vs. 1.5–3 cm long). It can be distinguished from O. grandibracteolata by the glabrous (vs. densely villous with trichomes multicellular or sometimes also unicellular) stems, the 5–8 cm long (rarely shorter) and glabrous peduncle (vs. 0.6–1.7 cm long and densely multicellular villous), and the 9–16 mm long corolla tube (vs. 22–25 mm long). It is different from O. liuyanii by the fact that most leaves are arranged in markedly unequal (vs. equal) pairs, the 5–8 cm long (rarely shorter) peduncle (vs 1–2 cm long), the longitudinally 5 - ridged corolla tube (vs. 5 - winged), and the glabrous (vs. pubescent) style in the long-styled flowers. The new taxon is also similar to O. cantonensis Hance by the length of the corolla. It differs from O. cantonensis by the congested-cymose (vs. paniculiform to corymbose) inflorescences, the ovate, oblong, or broadly ovate (vs. linear) bracteoles, and the spreading (vs. reflexed) corolla lobes. A detailed morphological comparison is shown in Table 1. An identification key to O. xishuiensis and its morphologically similar species is provided.

Key to Ophiorrhiza xishuiensis and its morphologically similar species

Ophiorrhiza typically prefers to grow near streams or in damp areas. Few people have paid attention to its sap. We examined the new taxon and O. japonica and found that the new taxon has a very small amount of white sap, while the latter has a very small amount of transparent, water-like sap, which becomes visible when cutting the petiole.

Ophiorrhiza often has colleters inside the stipules and calyx. However, the colleters inside or on the bracts and bracteoles have often been overlooked. We examined the new taxon and O. japonica and found that both have bracteoles with a single globose colleter (yellow in colour) on each side of the inner base. Sometimes, the new taxon has red sparse colleters on both the adaxial and abaxial surfaces of the bracteoles, as well as on the margin, while O. japonica has yellow sparse colleters. Further research on the presence / absence and position of colleters in the genus is needed to better understand the taxonomical value of this character.