Thismia melanomitra Maas & Maas (1987: 141)

Silva, Diego Ferreira Da, Engels, Mathias Erich & Soares-Lopes, Célia Regina Araújo, 2020, Novelties in Thismia (Thismiaceae) from South Brazilian Amazon with the description of a new species, Phytotaxa 429 (4), pp. 261-273 : 263-268

2. Thismia melanomitra Maas & Maas (1987: 141) . ( Fig. 3–4 )

Herb 4–8,2 cm tall. Roots 9,5–18,5 × ca. 0,2 cm, thickened, pale brownish. Tuber absent. Stem 2–6,5 × ca. 0,2 cm, white. Leaves 6–7, 2–6 × 1–2 mm, reduced, scattered on the stem, alternated, narrowly-triangular to deltoid, base decurrent, apex acute, white. Flower 1–1,8 × 1,2–1,6 cm, pedicellate; pedicel 5–6 × 2 mm, white; ovary ca. 5 × 6 mm, subrounded, 6-angular, white; flower tube 1,4 × 0,5 cm, oblanceoloid, cylindrical and 6–angular, black with the ovary and external tepals white, internal surface horizontally striated, stria salient; tepals in two different whorls (3+3), outer tepals 5–6 × 4–5 mm, laminar, ovate, base acute, apex rounded to obtuse; inner tepals ca. 7 × 2 mm, curved over the annulus, sub spatulate, base acute, adnate to each other at middle distal portion forming the mitre; mitre hexagonal, in dorsal view forming 6 triangles foveolate; annulus 2 mm length, rounded. Anther 1 mm length, elliptical; filament reduced. Stigma ca. 2 × 2 mm, general form pyramidal , white; lobes descendant with apex slightly curved to the center. Fruit 5–7 × 8 mm, whitish; pedicel ca. 2,3 × 0. 2 cm, estiolated, whitish.

Specimens examined: — BRAZIL. Mato Grosso: Alta Floresta: RPPN Cristalino, Taboca trail, Alluvial Ombrophilous Dense Forest , near to Cristalino river , 28 January 2016, fl., D. F. Silva & L. L. Mota 03 ( HERBAM) ; RPPN Cristalino, Taboca trail, Alluvial Ombrophilous Dense Forest, near to Cristalino river , 28 January 2016, fl., D. F. Silva & L. L. Mota 04 ( HERBAM) ; RPPN Cristalino, Doutor Haffer trail, Alluvial Ombrophilous Dense Forest, margin of Cristalino river , 26 December 2016, fl., fr., D. F. Silva & S. Sourell 37 ( HERBAM;) ; Fragment of Alluvial Ombrophilous Dense Forest, near to Teles Pires River , 17 March 2018, fr., D. F. Silva 52 ( HERBAM) ; Nova Bandeirantes: Sítio do Valdo , 2 March 2017, fl., R. S. Ribeiro 211 ( HERBAM) ; Sítio do Valdo , 2 March 2017, fl., fr., R. S. Ribeiro 213 ( HERBAM) ; Novo Mundo: RPPN Cristalino, Cacao trail, Ombrophilous Dense Forest , 4 January 2017, fl., fr., D. F. Silva & S. Sourell 19 ( HERBAM) ; RPPN Cristalino, Serra 2 trail, Ombrophilous Dense Forest , 14 January 2018, fl., D. F. Silva et al. 49 ( HERBAM) .

Geographic distribution:— Until this study the species was known only from a single collection from Ecuador ( Maas & Maas 1987; Govaerts 2019). Our collections therefore signify a new register of its geographic distribution for Brazil, and the Mato Grosso State.

Discussion:—The species may be recognized among other species of the study area by the absence of a tuberous stem; thickened roots (larger than 2 mm in diameter); leaves scattered on the stem; inner tepals adnate to each other forming a hexagonal mitre 6–foveolate in dorsal view; stigma with descendant lobes. Found flowering and fruiting between January and March.

Figures

FIGURE 3.—Thismia melanomitra—A. Flowering habit. B. Fruiting habit. C. Detail of sectioned stem. D. Leaf. E. Outer tepal. F. Front view of the flower, showing outer and inner tepals (mitre). G–H. Detail of inner wall of flower tube, frontal and side view, respectively. I. Anther. J. Stigma. K. Frontal view of fruit. Based on D.F. Silva 03. Drawing by M.E. Engels.

FIGURE 4.—Thismia melanomitra—A–B. Flowering habit. C–D. Side view of the flower, different angles. E. Dorsal view of the flower, showing mitre. F. Flower after falling of the perianth, showing stigma. G–H. Fruit. Photographs:A and F. Susanne Sourell; B–E and G–H. Luísa Lima e Mota.