Protologue Description: SANTESSONIA LAGUNEBERGII Sérusieaux & Wessels, sp. nov.

Thallus fruticosus, pallide cinereo-griseus, 1-2(-3) cm, altus, valde ad rupes affixus; rami ± cylindrící, 0.4-1.0 mm.; diam. plerumque simplices vel dichotome ramosi, ± recti, ad apotheciarum positionem geniculati, semper rigentes et fragillimi , laevigati vel pruinosi vel rugosi. Apothecia semper praesentia, lateralia, ± 1.0 mm diam, primo plana et marginata deinde hemisphaerica et reducta margine. Corticale stratum lacunosum cum numerosis mortuis cellulís; algae ± in glomerulís díspositae; centralís axis prosoplectenchymaticus, Excipulum pseudoparenchymaticum, nigro-brunneum; hymenium 90-110 µm crassum, hyalinum; hypothecium 20-30 µm crassum, nigro-brunneum; paraphyses simplices, ad basim anastomosantes et ad apicem ramosae; asci clavatí, 8-sporí; sporae ellípsoídeae, 1-septatae, ad Beltraminia-typum pertinentes sed cum toro et crassa paríete, (11-)l2-14(-15) x 7-8 µm . Pycnidia numerosa; conidia bacilliformía, 2-3 x 1 µm.Acidum psoromicum contínens.

Thallus fruticose, pale ash-gray, 1-2(-3) cm high, made of a bundle of 3 to 10 erect branches, firmly attached to the rocks by a rather thick and compact holdfast; branches cylindrical or slightly flattened, 0.4-1.0 mm in diam (measured at mid-height), ± even in diameter, usually simple or with an isotomicdichotomous branching pattern (branching angle acute), straight or little flexuose but always rigid, geniculate at the level of apothecía which are born laterally, apices attenuated. Surface smooth, or pruinose, or rugose due to the cortical abrasion, sometimes almost scaled and locally decorticated and then becoming dark grey or black. Thallus very fragile and brittle, even when moistened, especially near the base. Apothecía always present, usually plentiful, lateral, ± 1.0 mm in diam, sometimes up to 1.5 mm, at first plane and distinctly marginate with a dark blue disc covered by a white-blue pruina, soon becoming hemispherical, with a very reduced margin and without pruina. Apothecia often abraded and excavate, very rarely cerebriform. Cortical layer lacunose in typical conditions, especially near the outer surface. Phycobiont layer arranged in ± well-defined glomerules containing many dead cells interspersed with living ones. Central axis dense and compact, made of thick-walled periclinally arranged hyphae. Excipulum composed of radially arranged rows of parallel cells, cells dark brown; hymenium 90-110 µm thick, hyaline; hypothecium 20-30 µm thick, dark brown to dark violet, made of densely interwoven hyphae; paraphyses simple or rarely branched near the apices, anastomosed at their bases, apices distinctly inflated with dark brown walls; asci claviform, 8-spored; spores ellipsoid, (11-)12-14(-15) x 7-8 µm, 1-septate, at first blue-green with a smooth outer surface, then turning dark brown with a papillose outer surface, of the Beltraminia-type but with a distinct torus and an evenly thickened wall (less than 1 µm). Pycnidia frequent, but absent on a few thalli, appearing as small blackish sometimes aggregated knobs, partially and irregularly covered by the thallus cortex (their external appearance is thus quite variable); conidia mostly formed terminally from conidiogenous cells, following the phialid pattern, bacilliform to + ellipsoid, 2-3 x I µm. TLC : psoromic acid.
Type : SW Africa, Namibia, southern part of the Laguneberg Range, 2-3 km N of Myl 72 on the road going from Swakopmund to the Skeleton Coast Park, + 150 m, granite hill running parallel to the coastline, ± 6 km inland, 2.1983, Sérusiaux 5218 & Wessels (LG-holotype; Univ. North Pietersburg, BM, CZU, US, UPS, herb. Vézda-ïsotypes).

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