Thismia okhaensis LƯu, Tịch, G. Trần & Q.D. Đinh, 2014

Trư ờng, Lưu H ồng, T ịch, Nguy ễn Thi ện, Gi ỏi, Tr ần, Di ệp, Đinh Quang, Long, Vũ Ng ọc, Bách, Nguy ễn Lê Xuân, Dung, Ngô Th ị Thùy & Trung, Nguy ễn Thành, 2014, Thismia okhaensis (Thismiaceae) - a new fairy lantern from Vietnam, Phytotaxa 164 (3), pp. 190-194 : 190-193

Thismia okhaensis LƯu, Tịch, G. Trần & Q.D. Đinh , sp. nov. ( Figs. 1 & 2 ).

Allied to Thismia angustimitra Chantanaorr. and T. mirabilis K.Larsen in having vermiform roots, and suppressed outer tepals and connate inner tepals that form a mitre, but it differs in having a convex top mitre with three digitate furrows, involucral bracts with round apex, apertures totally hidden under the mitre, and connective appendages with lateral teeth.

Type:— VIETNAM. Khánh Hòa Province: Khánh SƠn District, Khánh SƠn Protection Forest, Ô Kha Valley , approximate coordinates 12° 2'57” N & 108°59'10" E, ca. 800 m elevation, 12 July 2013. Nguyễn Thiện Tịch, Trần Giỏi, Đinh Quang Di ệp, Lưu H ồng Trư ờng and Nguyễn Thành Trung KH 638B (holotype, SGN!) .

Herbs, terrestrial, achlorophyllous, mycotrophic, erect. Roots few, vermiform, unbranching, fleshy, white. Stems erect, simple, white, up to 13 cm tall, bearing 1 flower. Leaves scale-like, triangular, 3 mm long × 2 mm wide at base, appressed, translucent, apex acute. Involucral bracts 3, white, 7 mm long × 2 mm wide at base, appressed, apex round. Flowers ca. 30 mm long, perianth of 6 tepals, fused to form an obovate mitre, perianth tube 9–10 mm long, translucent black, bluish brown at base, with externally longitudinal stripes; outer tepals 3, white, ca. 4 × 6 mm, reflexed, furrowed, mucronate, margins entire; inner tepals 3, white, mitriform with three arch-shaped lateral apertures completely hidden under the mitre, aperture ca. 3 × 7 mm, with digitately furrowed convex top of mitre, glandular hairs under the top of mitre; annulus incurved; stamens 6, pendulous from the annulus, connate to form a tube hanging over the style, adaxially but not abaxially with glandular hairs, connective translucent light brown, plicate, broad with quadrangular appendage, appendage skirt-like, translucent yellowish brown, plicate, with two lateral teeth and glandular hairs; anthers oblong, 2 mm long, extrorse, adaxial on the basal part of the stamen; styles ca. 0.8 mm long; stigmas ca. 1.5 mm long, translucent bluish brown, deeply trilobed, papillose; ovaries inferior, patelliform, translucent white, top flat and bluish brown, 2.5 mm high, unilocular, placentas 3, free, fusiform, each joined at the apex and base of the locule by stalks; ovules numerous. Fruits unknown.

Habitat: —In damp soil between granite rocks under closed evergreen tropical forest at about 840 m elevation.

Distribution & IUCN preliminary assessment: —The species is very rare, only 3 individuals are known from the type locality even though we have been surveying biodiversity in whole Khánh Hòa Province and neighbouring provinces for many years. Our subsequent attempts to locate additional populations of the species yielded no results. As Ô Kha Valley is threatened by human encroachment and agricultural plantation, this species should be considered for placement in the Endangered category, EN B1ab(i,ii) ( IUCN, 2001).

Etymology:—The new species is named after the type location, Ô Kha Valley.

Notes:— T. okhaensis belongs to the section Sarcosiphon (Bl.) Jonk. (1938: 43) in having outer tepals suppressed and inner tepals connate to form a mitre. In the section, it appears to be closest to T. angustimitra Chantanaorr. (2008: 524) and T. mirabilis K. Larsen (1965: 171) , species both found in Thailand, in having vermiform roots and white outer tepals. However, T. okhaensis is readily distinguished from the two species in having involucral bracts with round apex, apertures completely hidden under the mitre, digitately furrowed convex top mitre, and connective appendage with lateral teeth ( Table 1 ).

Figures

FIGURE 1. Thismia okhaensis. A. Habit of the plant. B–C. Side views of flower. D. Longisection of whole flower. E. Longisection of ovary. F. Stamens. Drawn by Nguyễn Thiện Tịch based on fresh type specimens.

FIGURE 2. Thismia okhaensis. A. Habit of the plant. B. Individuals with erect vermiform roots. C. Leaf. D. Flower. E. Mitre, top view. F. Glandular hairs under the mitre. G. Flower, longisection. H. Stamens and appendages. I. Stigma, top view. J. Stigma and style, side view. K. Ovary, cross section. L. Placenta, longisection. Photos by Lưu Hồng Trường and Nguyễn Thiện Tịch.