Tupistra patula Averyanov 2016

Type:— VIETNAM. Ha Giang province, Bac Me district, Thuong Tan municipality, humid primary forest of evergreen broad-leaved trees on very steep slopes and along rocky ridge composed of solid crystalline highly eroded limestone at elevations 1200–1285 m a.s.l. around point 22°38′19.0′′ N, 105°17′06.5′′ E, not common, 16 November 2014, L. Averyanov, T. H. Nguyen, K. S. Nguyen, T. Maisak, L. Osinovets, CPC 7492 (holotype, Herbarium of the Center for Plant Conservation, Hanoi!; isotype, LE!).

Studied specimens:— VIETNAM. Ha Giang province, Quan Ba district, Tung Vai commune, Ban Thang village, secondary evergreen broad-leaved forest on rocky limestone mountain, under shaded places around point 23°03′18.8′′ N, 104°52′51.6′′ E, at elevation of 1100 m a.s.l., terrestrial or lithophytic perennial herb, flower white-purple, not common, 27 December 2016, N. S. Khang et al., NSK 845, Fig. 6 (HN!); Ha Giang province, Quan Ba district, Can Ty commune, Dau Cau 1 village, around point 23°05′27.3′′ N, 105°01′02.9′ ′ E, at elevation of 1120 m a.s.l., primary evergreen broad-leaved forest mixed with conifers (Xanthocyparis vietnamensis, Nageia fleuryi, Pseudotsuga sinensis, Calocedrus rupestris) at the top of rocky limestone mountain, usually in shaded places at the base of mountains, terrestrial or lithophytic perennial herb; inflorescence white-purple, tepals dull-green at tip and white at base when young, and dull-yellowish to white when old, common, 16 December 2016, N. S. Khang et al., VP 21 (HN!); Ha Giang province, Quan Ba district, Can Ty commune, Dau Cau 1 village, around point 23°05′27.2′′ N, 105°01′03.0′′ E, at elevation of 1160 m a.s.l. Primary evergreen broad-leaved forest mixed with conifers (Xanthocyparis vietnamensis, Nageia fleuryi, Pseudotsuga sinensis, Calocedrus rupestris) at the top of rocky limestone mountain, usually in shaded places at the base of mountains, terrestrial or lithophytic perennial herb; inflorescence white-purple, tepals dull-green at tip and white at base when young, and dull-yellowish to white when old, common, 16 December 2016, N. S. Khang et al., VP 22 (HN!); Ha Giang province, Quan Ba district, Can Ty commune, Dau Cau 1 village, around point 23°05′45.1′′ N, 105°01′02.7′′ E, at elevation of 1050 m a.s.l., primary evergreen broad-leaved forest mixed with conifers (Xanthocyparis vietnamensis, Nageia fleuryi, Pseudotsuga sinensis, Calocedrus rupestris) at the top of rocky limestone mountain, usually in shaded places at the base of mountains, terrestrial or lithophytic perennial herb; inflorescence white-purple, tepals dark brown to black when dried, common, 17 December 2016, N. S. Khang et al., VP 25 (HN!); Ha Giang province, Quan Ba district, Thanh Van commune, Ma Hong village, around point 23°06′24.1′′N, 104°58′42.1′′E, at elevation of 1000 m a.s.l., primary evergreen broad-leaved forest of rocky limestone mountain, in shaded places at base of mountains, terrestrial or lithophytic perennial herb; inflorescence white-purple, tepals dark brown to black when dried, not common, 18 December 2016, N. S. Khang et al., VP 031 (HN!); Ha Giang province, Quan Ba district, Can Ty commune, Dau Cau 1 village, around point 23°06′20.5′′ N, 105°01′04.5′′ E, at elevation of 1100 m a.s.l., Primary evergreen broad-leaved forest mixed with conifers (Xanthocyparis vietnamensis, Nageia fleuryi, Pseudotsuga sinensis, Calocedrus rupestris) at the top of rocky limestone mountain, in shaded places at the middle of mountains, terrestrial or lithophytic perennial herb; inflorescence white-purple, tepals dark brown to black when dried, very common, 19 December 2016, N. S. Khang et al., VP 52 (HN!).

Habitat and phenology:—Primary and secondary evergreen broad-leaved, mixed and coniferous forests (with Xanthocyparis vietnamensis, Nageia fleuryi, Pseudotsuga sinensis, Calocedrus rupestris) on rocky solid highly eroded karstic limestone at elevations 1100–1300 m a.s.l. Lithophytic herb on mossy rocks on rocky steep slopes, often in shady and humid places. Flowering in October–December.

Distribution:—Northern Vietnam (Ha Giang province, Bac Me & Quan Ba districts). Local endemic to northern Vietnam.

Notes:—The original description of Tupistra patula was based on specimens with rather aged inflorescences. The perigone was reported as dull yellow (Averyanov et al. 2016a). In December 2016, we collected plants of this species again at several localities in Ha Giang province, northern Vietnam. Some of the plants had a small number of floral buds on the distal part of their inflorescence rachis. The buds were white proximally, dull greenish purple distally. The perigones of young fully open flowers were, internally, white proximally and pale green distally including segments, externally white slightly tinged with purple proximally, dull greenish purple distally. Anther-sacs and pollen were yellow. Somewhat faded flowers passing their peak had dull whitish beige perigones (externally slightly tinged with purple). With fading the perigones turn to be darker, and eventually become blackish (Fig. 6; Averyanov et al. 2016a). The styles and stigmas were more or less whitish at the early and middle stages of flowering, but later, through beige stages, turn to be darker, as in perigones. The flowering stems were more or less erect and straight, hence the sigmoid, outspreading floriferous stem reported earlier (Averyanov et al. 2016a) appears not to be a stable characteristic of this species. All collections hitherto made indicate that the distribution range of this species is confined to Ha Giang province, northeastern Vietnam.