Placolecis sublaevis

Placolecis sublaevis has a crustose (crust-like) to effigurate (radiating) thallus. In the centre, it has an areolate-squamulose (divided into small, scale-like sections) structure, forming irregular patches or clumps. The thallus incorporates numerous pseudopycnidia (false conidiomata, a type of asexual reproductive structure) that are immersed within it. The lobes of this lichen distinctively form larger aggregations at the margins, measuring 2–3 (occasionally up to 4) mm long and 0.1–0.3 mm wide in the middle, slightly widening towards the tips to 0.15–0.4 mm. These lobes are dark brown and slightly flattened at the apex, often with secondary lobules branching from the main lobes and reaching 1–2 mm in length.^[1]

The lichen's upper surface is dark brownish with an uneven texture. Its upper cortex, the outermost layer, is 12.5–20 μm thick with a paraplectenchymatous (loosely interwoven) structure. The algal layer is diffuse, spanning 25–40 μm in thickness, with Trebouxia-like photobiont (symbiotic green algae) cells measuring 6–12 μm in diameter. The medulla (the inner tissue of the thallus) varies in thickness from 60 to 140 μm and shows a reddish-orange colouration in the upper portion, transitioning to white in the lower portion. This species does not have a lower cortex, nor does it have apothecia (fruiting bodies).^[1]

Reproductive structures, known as pycnidia, are numerous and immersed within the thallus. They measure 75–95 by 40–60 μm, are urceolate (jug-shaped), and have a black ostiole (opening). The conidia (asexual spores) of this species are bacilliform (rod-shaped) and measure 5–6 μm.^[1]

In terms of reactions to standard chemical spot test, the medulla of Placolecis sublaevis is K+ (violet) in its upper yellow part, as well as P− and C−. Chemical analysis using thin-layer chromatography shows the presence of fragilin, solorinic acid, and anthraquinones.^[1]

This species is found in the high mountain regions of Yunnan and Sichuan in southeast China, specifically on exposed steep slopes adorned with limestone boulders near streams.^[1]