Thelenella

The genus was circumscribed by the Finnish lichenologist William Nylander in 1855, with Thelenella modesta assigned as the type species. In his original description, Nylander characterised Thelenella by its pore-like fruiting bodies with an immersed perithecium that was either uncoloured or only superficially pale. He noted that the spores were somewhat large, oblong, and multicellular, whilst the gelatinous hymenium remained entirely colourless. Nylander distinguished the genus as morphologically distinct, noting that the fruiting bodies were quite different from those of Verrucaria. ==Description==

Thelenella forms an inconspicuous, crust‑like thallus that lies tightly attached to its substrate and ranges from thin, membranous patches to cracked or warted crusts in dull whitish, pale grey, or light brown tones. The photosynthetic partner is a minute, spherical green alga of the type, evenly distributed through the fungal tissue. Sexual reproduction takes place in thick‑walled perithecia that are mostly immersed in the thallus. Their outer wall () is built of long, narrow cells arranged either lengthwise or in a tangled mesh; the pigment is evenly spread through this wall or diffused in a surrounding gel, never appearing grainy under high magnification. A second, darker protective layer () is rarely developed. Inside, the hymenial gel shows no reaction to iodine (I–, K/I–). Delicate, thread‑like branch and fuse, especially near their bases and tips, but they may be absent around the apical pore. The asci are , meaning they have two functional wall layers: a thin inner and a thicker outer one; they usually carry no iodine‑positive structures and contain two to eight ascospores. The spores themselves are colourless to slightly brown, with multiple cross‑walls that give them a somewhat to strongly muriform appearance; their outer wall is only marginally thicker than the septa. Asexual propagation is achieved by Roccella‑type pycnidia embedded in the thallus, which release colourless, rod‑shaped conidia lacking internal septa. No secondary metabolites (lichen products) have been detected in Thelenella species by thin-layer chromatography. ==Ecology==

Species of Thelenella occupy a wide range of damp, shaded substrates. They most often grow directly on tree bark (corticolous) but can also colonise living leaves (foliicolous), bryophyte cushions on foliage (bryophilous), shaded rock faces (saxicolous), and patches of moss-rich soil (terricolous). ==Species==

, Species Fungorum (in the Catalogue of Life) accepts 22 species of Thelenella. • Thelenella brasiliensis • Thelenella calcicola • Thelenella cinerascens • Thelenella fugiens • Thelenella fusispora – Tanzania • Thelenella geminipara • Thelenella haradae – South Korea • Thelenella humilis • Thelenella indica – India • Thelenella inductula • Thelenella justii • Thelenella kerguelena • Thelenella larbalestieri • Thelenella lateralis • Thelenella luridella • Thelenella luzonensis • Thelenella marginata • Thelenella mawsonii • Thelenella melanospora • Thelenella modesta • Thelenella monospora – Brazil • Thelenella muscorum • Thelenella nubifera • Thelenella philippina • Thelenella rappii • Thelenella sampaiana • Thelenella sastreana • Thelenella sychnogonioides • Thelenella tasmanica • Thelenella vezdae • Thelenella weberi ==References==