Fungal Divers. (online version), 64: 286, 2013. Basionym: Collema pulposum var. ligerinum Hy - Mèm. Soc. Nat. Agricult. Sc. Arts Angers: 24, 1893.
Synonyms: Collema ligerinum (Hy) Harm.; Collema verruculosum auct. p.p.; Lathagrium conglomeratum sensu A. Massal.; Leptogium verruculosum (A. Massal.) Jatta
Distribution: N - VG, Frl (Castello & Skert 2005), Ven, TAA (Nascimbene & al. 2007b), Lomb (Brusoni & al. 1997, Brusoni & Valcuvia 2000), Piem (Piervittori 2003, Isocrono & al. 2004), VA (Piervittori & Isocrono 1999), Emil (Fariselli & al. 2020), Lig (Giordani & al. 2009, Giordani & Incerti 2008). C - Tosc, Marc (Nimis & Tretiach 1999, Frati & al. 2004, Frati & Brunialti 2006, Brackel 2015), Umb (Ravera 1998, Ravera & al. 2006, Brackel 2015), Laz, Abr (Recchia & al. 1993, Olivieri & al. 1997, 1997b, Loppi & al. 1999, Gheza & al. 2021), Mol (Caporale & al. 2008). S - Pugl, Bas (Nimis & Tretiach 1999), Cal (Puntillo 1996, Puntillo & Puntillo 2004, Incerti & Nimis 2006).
Description: Thallus small-foliose to subsquamulose, homoiomerous, gelatinous when wet, 5-10 mm wide, forming rounded cushions. Lobes few, 0.5-1.5 mm wide, flattened, adpressed to erect, usually branched, distinctly swollen. Upper surface dark olive-green to brown or black, dull, epruinose, without isidia; lower surface usually paler. Upper and lower cortices absent. Apothecia crowded, often hiding the lobes, sessile, with constricted base on lobe margins or terminal 0.5-1(-2) mm across; disc plane to convex, dark reddish brown; thalline margin rather thick, eventually disappearing, entire, smooth. Proper exciple euthyplectenchymatous; hymenium colourless, 70-80 µm tall. Asci 8-spored, clavate, the apex thick, with a I+ blue apical dome and a I+ blue annulus projecting downwardly. Ascospores 3-septate, hyaline, ellipsoid with rounded ends, slightly restricted at septa, 14.5-22.5 x 6-8.5 µm. Pycnidia common, immersed, globose. Conidia bacilliform, slightly swollen at the ends. Photobiont cyanobacterial (Nostoc), in long chains. Spot tests: all negative. Chemistry: without lichen substances.
Note: a mild-temperate species found on base-rich bark, especially of Juglans and Populus; more widespread in the past, but locally still common near small settlements in montane valleys, e.g. in the eastern Pre-Alps. It is included in the Italian red list of epiphytic lichens as “Near-threatened” (Nascimbene & al. 2013c).