Ophiorrhiza hainanensis Y. C. Tseng (1974: 582)

Liu, Wen-Jian, Gao, Qi, Nguyen, Khang Sinh, Nguyen, Dzu Van & Wu, Lei, 2020, Taxonomic studies on Ophiorrhiza in Vietnam I: Ophiorrhiza hiepii and O. hainanensis, a new species and new record from northern Vietnam, Phytotaxa 429 (1), pp. 65-72 : 70-71

Ophiorrhiza hainanensis Y. C. Tseng (1974: 582) ( Fig. 3 & 4A–D )

Type: — CHINA. Hainan province: Qiongzhong county, Wuzhi mountain, alt. 255 m, wet places, 23 December 1933 (fr.), Zhi Huang 35832 (type: IBSC [0473465]!).

Herbs, ascending, 15–30 cm tall; stems puberulent with unicellular trichomes. Leaves in subequal pairs; petiole 0.5–1.5 cm, puberulent; blade drying thinly papery, adaxially dark green, abaxially pale green, elliptic to ovate, 4.5–13 × 2.5–5.5 cm, adaxially glabrous, abaxially pilosulous along principal veins, base obtuse to acute, margins entire, apex acuminate to shortly caudate; secondary veins 7–13 pairs; stipules persistent, triangular, usually 2-lobed; lobe 3–10 mm long, aristate-acuminate. Inflorescence congested-cymose, several flowered, puberulent; peduncles 0.5–1 cm, stout; bracts narrowly oblong, 5–11 mm, viscid ciliate. Flowers homostylous with stigma and anther both included at or a little above the middle of corolla tube. Calyx sparsely puberulent; hypanthium 1.8–2.2 × 2–3 mm; lobes triangular, to ca. 1 mm. Corolla tubular, glabrous outside, densely pubescent at throat of corolla tube inside; tube 5–8 mm long; lobes triangular-ovate, 1.8–2.2 × ca. 1.5 mm. Stamens 5; anthers 1.4–1.6 mm long, linear, dorsifixed, dehiscing longitudinally. Stigmas 2-lobed; lobe lanceolate, ca. 2.5 mm. Capsules obcordate, ca. 3–5 × 6–9 mm, sparsely puberulent. Seeds many, angular.

Phenology: —Flowering March to June, fruiting July to December.

Conservation status: —Because the populations found in Vietnam and China are with large numbers of individuals and distributed in protected areas, we estimate that this species will not become extinct. Thus, following the IUCN red list categories and criteria (2016), the conservation status of this species is Least Concern ( LC).

Specimen data: ― VIETNAM. Vinh Phuc Province: Tam Dao National Park , 21°27′31″N, 105°38′31″E, alt. 1049 m, 25 October 2017, Nian He Xia, Jing Bo Ni, Yi Hua Tong & Xi Rong, TYH-1325 ( CSFI, IBSC) ; Vinh Phuc Province, Tam Dao National Park , 21°27′38.19″N, 105°38′56.13″E, alt. 950 m, 18 May 2018, Lei Wu, Qi Gao, Su Juan Wei, Van Dzu Nguyen & Thinh , VN 0001 ( CSFI, HN, ten duplicates) .

Discussion:— Ophiorrhiza hainanensis , previously known only from China, was published by Tseng (1974) based on five collections from Wuzhi mountain of central Hainan, all of which are fruiting materials or with flower buds. However, the species is distinguishable by its persistent and triangular stipules with aristate-acuminate apex and congested-cymose infructescence with peduncles 0.5–1 cm long, elliptic-oblong to oblong bracts and several compressed capsules. During our plant surveys of Tam Dao National Park in Vinh Phuc Province, both flowers and fruits of this species were discovered. Therefore, we report this species as a new record for the flora of Vietnam and measured its mature flowers, which were totally unknown before, in the wild for the supplemental description of the floral characters.

Owing to their similar vegetative appearance as well as the insufficient information of O. hainanensis in flower, the relationship between O. hainanensis and Ophiorrhiza nutans C. B. Clarke ex J. D. Hooker (1880: 84 , Fig. 2E–H ) has always been confusing. Lo (1999) differentiated these two taxa by the indumentum covering the plant and the number of the secondary veins, viz. O. hainanensis has unicellular pubescence on most surfaces of its plant parts and leaves with secondary veins 15–17 pairs while O. nutans has dense and multicellular trichomes and leaves with 9–15 pairs secondary veins.After examining specimens of both taxa, however, Duan and Lin (2007) concluded that these two were conspecific because the range of variation of the above characters overlap with each other for some specimens, and hence O. hainanensis was reduced to a synonym of O. nutans . Despite noticing the revision work, O. hainanensis was provisionally retained as a different species from O. nutans in the recently published work by Chen and Taylor (2011), based on the color of the plant after drying and the distribution other than the diagnostic characters given by Lo (1999). In the present study, we confirm that O. hainanensis and O. nutans are two distinct species. O. hainanensis can be recognized from O. nutans by its peduncles which are 0.5–1 cm long (vs. 1–6 cm long), homostylous flowers (vs. distylous), stigma and anthers which are both included at or a little above the middle of corolla tube (vs. stigma at the throat while anthers a little below the middle of corolla tube in the long styled flower, and stigma inserted at 1/3 lower part while anthers near 2/3 upper part of corolla tube in the short styled flower).

Figures

FIGURE 2. Ophiorrhiza hiepii L.Wu, Q. Gao & K.S. Nguyen.A.Habit; B. Flowers in side view; C. Inflorescencesin side view; D. Opened short-styled flower; E. Opened long-styled flowers; F. Infructescence in side view. O. subrubescens Drake. G. Habit; H. Inflorescences in side view; I. Opened short-styled flower; k. Opened long-styled. Scales: B, D, E=5 mm, C, F, H, I, K=1 cm. Photographed by L. Wu and K.S. NGUYEN.

FIGURE 3. Ophiorrhiza hainanensis Y. C. Tseng. A. Habit; B. Flower in side view; C. Flower in face view; D. Opened flower. Drawn from Lei Wu, Qi Gao, Su Juan Wei, Van Dzu Nguyen & Thinh, VN0001 by Bi-Shan Li.

FIGURE 4. Ophiorrhiza hainanensis Y. C. Tseng. A. Habit; B. inflorescence in side view; C. Opened flower; D. Infructescence in side view. O. nutans C. B. Clarke ex J. D. Hooker: E. habit; F. inflorescence in side view; G. Opened long-styled flower; H. Opened short-styled flower. Scales: 5 mm. Photographed by L. Wu.