Immersaria venusta

The body (thallus) is crustose and areolate, forming a continuous crust that is brown to orange-brown and often rusty in tone. Individual areoles are irregular, often tending towards a rectangular outline, typically 0.5–1.3 mm across, and flat to slightly convex. They are commonly cracked and may be frosted (pruinose), while the thallus margin is also frosted. No distinct border zone (prothallus) was observed in the material studied.^[2]

The fruiting bodies (apothecia) are frequent and often crowded, usually sunken in the thallus (though they may appear slightly separated from the areoles), and measure about 0.6–1.0 mm in diameter. The disc is black and flat, without frosting; the margin is reduced but can sometimes be more developed. Under the microscope, the uppermost tissue layer (epihymenium) is brown, and the asci are of the Porpidia-type, each containing eight spores. The ascospores are simple (undivided), oval (ellipsoid), surrounded by a clear halo (halonate), and measure about 10.0–12.5 × 5.0–7.5 μm. The asexual fruiting structures (conidiomata) are sunken, linear, and black with a frosted margin, but asexual spores (conidia) were not observed. Spot tests on the thallus are K− and C−, while the inner tissue (medulla) stains violet with iodine (I+ violet). The chemistry is variable: specimens contained confluentic acid (often with 2'-O-methylmicrophyllinic acid), or planaic acid, or (rarely) no detected substances.^[2]

Immersaria venusta is saxicolous, growing on rock including quartz sandstone and granite. It has been collected in alpine climates at elevations of about 3,900–4,300 m. The material treated in the revision comes from western China, with collections from Qinghai Province (including the type locality) and additional specimens cited from Sichuan Province.^[2]