Parnassia wightiana Wallich ex Wight & Arnott (1834: 35)

Pham, Ngoc Hoai, Ren, Ming-Xun, Nuraliev, Maxim S., Trinh, Ngoc Bon, Nguyen, Tien Dat, Ragupathi, Gopi & Pham, Van The, 2022, The genus Parnassia in Vietnam, and a checklist of Vietnamese Celastraceae, Phytotaxa 536 (3), pp. 213-227 : 215-217

1. Parnassia wightiana Wallich ex Wight & Arnott (1834: 35) ( Figs. 2–4 )

References: Grierson (1987: 517), Gu (1987: 46), Gu & Hultgård (2001: 114), Suksathan (2009: 46), Bhaskar & Shinobu (2012: 1), Shu et al. (2017: 6), Wang et al. (2018: 133), Averyanov et al. (2020: 282).

TYPE: — INDIA. Sine loc., R. Wight 116 (lectotype, designated by Shu et al. [2017: 6]: K: 000739468 photo!; isolectotypes: E: E00174108 photo!, E00174109 photo!, E00174110 photo!; GZU: 000100142; K: 000739466 photo!; P: P00709377 photo!) .

Description (based on Vietnamese specimens):—Herbs perennial, forming dense clumps, generally glabrous. Rhizome 2–4 cm long, 1.0– 1.5 cm in diam., with numerous roots. Basal leaves 8–10, 11– 15 cm long; petiole 8–13 cm long, 1.5–2 mm in diam., adaxially grooved, winged at base, wings sheath-like, 2 cm long and 1 mm wide; blade adaxially dark green, abaxially light green, broadly cordate to reniform, 2.5–4.5 × 3.0– 6.5 cm, base cordate, apex rounded to obtuse with short mucro, margin entire, with 9–11 veins pedately originating at base. Floriferous stem subterminal (arising near the rhizome apex), usually 1, stout, angled, to 20 cm long, 2.0 mm in diam. Cauline leaf 1, at middle of floriferous stem, nearly sessile; blade similar to that of basal leaf in shape but smaller, with several dark brown hairs at margin near base. Inflorescence 1-flowered. Flower 4 cm in diam.; hypanthium short, 6 mm wide. Sepals 5, light green to yellowish, broadly oblong, 10–12 × 4.5–6.0 mm, slightly narrowed towards base, apex obtuse, with margins decurrent onto inferior part of ovary, with some inconspicuous parallel veins. Petals 5, white with bright green base on adaxial side (especially so at vein bases), broadly obovate, 15–19 × 13–15 mm, with a claw 2.0–3.0 mm long; apex rounded and slightly lobed, blade margin at its basal 2/3 with long branched fimbriations or more rarely erose. Stamens 5; filament 6–9 mm long, 1 mm in diam.; anther 2.5–3.0 mm long, 1.5 mm in diam., longitudinally dehiscent. Staminodes 5, flat, 5–6 mm long, 2.0– 2.5 mm wide at base, up to 4.5 mm wide distally, 5–7-lobed for up to almost 2/3 of their length; lobes spreading laterally, unequal in size, 2–3 mm long, 0.3–0.5 mm in diam., with distinct glands at apex (resembling toes of tree frog). Gynoecium of 3 united carpels; ovary semi-inferior; inferior part 5.5 mm high; superior part conical, obtusely three-angled, 3.5 mm high, 3.5 mm in diam. at base; style 1.5 mm long, 1 mm wide, bearing 3 short stigmatic lobes. Capsule triangular pyramidal, dehiscing into 3 valves; mature fruit 6 mm high, 6.5 mm wide at base. Seeds numerous, oblong, 1 mm long, 0.5 mm in diam.

Specimens examined: — VIETNAM. Ha Giang Province: Quan Ba District, Tung Vai commune, disturbed primary evergreen forest on limestone mountain, around point 23°04’03.1’’N 104°50’23.9’’E, at elevation of 1297 m, 17 March 2018, Pham Van The, Trinh Ngoc Bon TB 069 ( VAFS) ; Ha Giang Province: Quan Ba District, Tung Vai commune, Thang village , around point 23°03’13.4’’N 104°51’48.8’’E, steep rocky slopes of stream valley composed with eroded stratified highly eroded limestone at elevation 1000–1200 m a.s.l., primary evergreen broad-leaved very humid forest, open wet mossy river rocks, 23 April 2018, L. Averyanov, Nguyen Sinh Khang, Nguyen Tien Hiep, Nguyen Quang Hieu, Chuong Quang Ngan, T. Maisak VR 760 ( LE: LE01050109 http://en.herbariumle.ru/?t=occ&id=3978) ; Ha Giang Province: Quan Ba District, Tung Vai commune, Thang village , around point 23°03’00.4’’N 104°52’02.2’’E, steep rocky slopes of river valley composed with eroded limestone at elevation 1000–1060 m a.s.l., remnants of primary evergreen broad-leaved very humid forest, wet grassy places along river and on mossy open wet stream rocks, 19 October 2018, L. Averyanov, Nguyen Sinh Khang, T. Maisak, Truong Quang Ngan VR 1045 ( LE: LE01048857 http://en.herbariumle.ru/?t=occ&id=576, LE01049038 http://en.herbariumle.ru/?t=occ&id=4903, LE01049078 http:// en.herbariumle.ru/?t=occ&id=4918) ; Ha Giang Province: Quan Ba district, Ta Van commune, Can Ho village , around point 23.03513°N 104.87016°E, steep rocky mountain slopes composed of eroded limestone at elevation 1100– 1250 m a.s.l., secondary evergreen broad-leaved humid forest along rocky stream, open wet mossy stream rocks, 9 October 2019, L. Averyanov, Nguyen Sinh Khang, T. Maisak VR 1494 ( LE: LE01066941 http://en.herbariumle. ru/?t=occ&id=12724, photos LE01061037 http://en.herbariumle.ru/?t=occ&id=13091) ; Yen Bai Province: Mu Cang Chai District, Nam Co commune, Lung Cung village , secondary evergreen broad-leaved woodland and scrub, around point 21°54’23.5’’N 104°16’59.4’’E, at elevation of 1762 m, 22 September 2011, Pham Van The, Nguyen Tien Vinh, Hoang Van Than CPC 4488 ( CPC – Herbarium of the Center for Plant Conservation, Vietnam Union of Science and Technology Associations, Hanoi, Vietnam; photos LE: LE01087319 http://en.herbariumle.ru/?t=occ&id=27233) .

Distribution: — Afghanistan, N India, Nepal, Bhutan, China, N Thailand, N Vietnam (Ha Giang and Yen Bai provinces).

Phenology: —In Vietnam, flowering was observed from March to October, fruiting was observed from April to October.

Habitat and ecology: —In Vietnam, Parnassia wightiana was found in wet places along streams in disturbed primary evergreen forest on limestone, and also in secondary evergreen broad-leaved woodland and scrub on nonlimestone mountains at elevations of 1000–1760 m, as a lithophyte or a terrestrial herb (see Fig. 1 ). Parnassia wightiana is known from several populations within Vietnam, some of which contain numerous individuals ( Averyanov et al. 2020; this study).

In the secondary forests with Taiwania cryptomerioides in Yen Bai Province, P. wightiana (the specimen Pham et al. CPC 4488) grows together with Dicranopteris linearis (Gleicheniaceae) , Asplenium sp. (Aspleniaceae) , Amorphophallus sp. (Araceae) , Carex sp. (Cyperaceae) , Rubus sp. (Rosaceae) , Melastoma sp. (Melastomataceae) , Ageratina adenophora (Asteraceae) .

In the limestone landscape of Ha Giang Province, P. wightiana (the specimen Pham Van The, Trinh Ngoc Bon TB 069) was recorded to grow together with the following herbs and small understorey woody plants: Equisetum diffusum (Equisetaceae) , Dryopteris stenolepis (Dryopteridaceae) , Pyrrosia bonii (Polypodiaceae) , Acorus calamus (Acoraceae) , Tacca integrifolia (Taccaceae) , Nervilia fordii (Orchidaceae) , Caryota urens (Arecaceae) , Anemone sumatrana (Ranunculaceae) , Ficus abelii (Moraceae) , Elatostema dissectum (Urticaceae) , Begonia lecomtei (Begoniaceae) , Micromelum minutum (Rutaceae) , Maesa montana (Primulaceae) , Ophiorrhiza baviensis , O. japonica (Rubiaceae) . The primary forest at high elevations in that area comprises tree species including Fokienia hodginsii (Cupressaceae) , Amentotaxus yunnanensis , Taxus chinensis (Taxaceae) , Magnolia coriacea , M. grandis (Magnoliaceae) , Actinodaphne ellipticibacca , Cinnamomum parthenoxylon , Phoebe macrocarpa (Lauraceae) , Mahonia nepalensis (Berberidaceae) , Castanopsis cerebrina , Lithocarpus balansae , Quercus platycalyx (Fagaceae) , Aucuba japonica (Garryaceae) ; understorey woody plants include Gomphandra mollis (Stemonuraceae) ; herbs include Paris polyphylla (Melanthiaceae) , Paphiopedilum hirsutissimum , P. micranthum (Orchidaceae) , Dysosma difformis (Berberidaceae) ; vines include Stephania tetrandra , Tinospora sagittata (Menispermaceae) , Jasminum elongatum (Oleaceae) ; epiphytes include Rhaphidophora decursiva (Araceae) , Coelogyne lockii , Dendrobium chrysanthum , Eria scabrilinguis (Orchidaceae) .

Notes: — Gu & Hultgård (2001) indicated considerable morphological variability of Parnassia wightiana manifested, in particular, in differences in leaf shape and flower size between populations from different regions of China. The recently proposed ample synonymy of P. wightiana ( Shu et al. 2017, Wang et al. 2018) should also contribute to the variation ranges of its characters. Our study extends further the known morphological diversity of the species, as compared with its earlier published descriptions ( Grierson 1987, Gu & Hultgård 2001, Bhaskar & Shinobu 2012). The Vietnamese specimens are remarkable in their numerous (8–10 vs. 2–5) basal leaves with larger number of veins (9–11 vs. 7–9), and larger flower parts, including sepals 10–12 mm (vs. 5–10 mm) long, petals 15–19 mm (vs. 8–15 mm) long, anthers 2.5–3 mm (vs. 1.5–2.5 mm) long. A detailed comparison is presented in Table 1 .

Figures

FIGURE 1. Distribution of the species of Parnassia in Vietnam.

FIGURE 2. Parnassia wightiana in natural habitats. A. Terrestrial habit in Yen Bai Province. B. Epilithic habit on limestone in Ha Giang Province. Pham Van The et al. CPC 4488 (A) and Pham Van The et al. TB 069 (B). Photos by V.T. Pham.

FIGURE 3. Parnassia wightiana. A. Plant with flower and fruit. B. Floriferous stem. C. Rhizome. D. Cauline leaf, adaxial and abaxial views. E. Basal leaf, adaxial and abaxial views. F. Flower, top view. G. Flower, side view. H. Flower, oblique view. Pham Van The et al. TB 069 (A–E) and Pham Van The et al. CPC 4488 (F–H). Photos by V.T. Pham.

FIGURE 4. Parnassia wightiana, floral morphology. A. Calyx, adaxial and abaxial views. B. Petals, adaxial view (upper row) and abaxial view (lower row). C. Stamens. D. Staminodes. E. Central part of flower showing staminodes and gynoecium, top and side views. F. Gynoecium at early anthesis, side view (outer floral organs removed). G. Immature capsule, side view. H. Immature capsule, cross section. I. Dehisced capsule, top view. J. Immature seeds. Pham Van The et al. TB 069 (A–D, F–J) and Pham Van The et al. CPC 4488 (E). Photos by V.T. Pham.