Thismia sect. Mirabiles Nuraliev, 2025

Nuraliev, Maxim S. & Sennikov, Alexander N., 2025, A new section in Asian Thismia (Thismiaceae), T. sect. Mirabiles, and its checklist, Phytotaxa 682 (3), pp. 259-266 : 261

Thismia sect. Mirabiles Nuraliev , sect. nov.

Diagnosis: —The new section is defined by the following combination of structural traits that is unknown in the remaining species of Thismia : underground organs represented by vermiform roots, inner tepals fused into a mitre, appendages of the inner tepals absent or not longer than ca. 1.5 mm, appendages of the stamens present, transverse bars of the inner surface of the hypanthium absent.

Type species: — Thismia mirabilis Larsen (1965: 171) .

Description:—Herbs up to 14 cm tall. Underground part represented by creeping vermiform roots. Flowers terminal and solitary or in terminal few-flowered monochasial inflorescence (more precisely, a thyrsoid with a single cyme), surrounded by involucre of usually 3 bracts (sometimes 2 bracts in lateral flowers), actinomorphic. Flowers usually coloured with white combined with dark to blackish blue/brown/green, with orange stamen appendages and sometimes certain other flower parts. Hypanthium inner surface without transverse bars, sometimes foveolate (described as “fenestrated” by Nuraliev et al. 2020, 2021) or irregularly reticulate. Annulus usually dome-shaped to erect, fleshy. Outer tepals present, distinct (never vanishingly small), unappendaged. Inner tepals postgenitally fused into a fleshy mitre, unappendaged or with small protuberance-like appendages up to ca. 1.5 mm high at mitre top (appressed to each other to form an apical mucro); mitre without foveae or with three foveae on upper surface. Mitre with valvate tepal aestivation. Stamens laminar, with long supraconnectives, fused postgenitally into a stamen tube. Supraconnective with adaxial skirt-like or wing-like appendage, with rounded or emarginate apex usually bearing several (up to 10) papillae. Interstaminal glands present (unverified for T. aurantiaca ). Thecae surrounded by rows of glandular hairs. Placentas parietal, becoming column-like by detachment from ovary wall (unverified for T. aurantiaca ); stylar column bearing 3 free styles; styles upright, usually rectangular. At fruit maturation, hypanthium abscising circumscissily. Fruit cup-shaped (a pyxidium), dehiscing apically by withering; pedicel sometimes moderately elongating during fruit maturation.

Etymology: —The name of the section is a plural form of the epithet of its type species, T. mirabilis . Thismia mirabilis is the first species of the section that has become known to science.

Notes: —The description follows the terminology suggested by Nuraliev et al. (2021), along with their findings on morphology of one of the species belonging to this section, T. mucronata .

Several species of Thismia sect. Mirabiles were observed to perform an unusual change of flower coloration immediately after immersion of the plants into alcohol: all the dark parts of the flower become intensively orange to red ( Larsen 1965, Nuraliev et al. 2014, Phonepaseuth et al. 2024). Here we provide for the first time an illustration of this phenomenon ( Fig. 1 ). This feature likely indicates the presence of a remarkable biochemical character in Thismiaceae . It has never been reported for any other representatives of the family, and its occurrence throughout Thismiaceae is still to be explored. The available images suggest a similar colour change in T. bryndonei Tsukaya, Suetsugu & Suleiman (2017: 135 , Fig. 1E–G ).

Distribution: — India (Andaman Islands), Laos, Thailand, Vietnam ( Fig. 2 ).

Four out of eight species of the section are known to be narrow endemics restricted to their type localities. Within each of the remaining four species, the distance between the known populations does not exceed 300 km.

Figures

FIGURE 1. Inflorescences of Thismia mucronata. A. Living plant. B. Plant immediately after immersion into alcohol. Photos by M. Nuraliev from the specimen Nuraliev 1009 (MW).

FIGURE 2. Distribution map of the species of Thismia sect. Mirabiles.