Description
Species of Toensbergia spread as pale granular crusts that can merge into extensive patches or, in sheltered spots, develop into slightly raised, scale-like lobes (subsquamulose thalli). Fresh material appears grey-white through cream to a faint green tint, depending on moisture and the density of the embedded green algal partner (a chlorococcoid photobiont with rounded cells). A separate hypothallus —the dark fungal fringe that rims many crustose lichens—is usually absent, but some specimens show a bluish-grey to charcoal border where the fungus grows beyond the photosynthetic layer. Asexual propagules dominate: powdery soredia erupt from tiny nipple-like bumps on the surface, while even finer, coral-shaped blastidia break away en masse, allowing the lichen to colonise nearby soil, mossy rock, or conifer bark without relying on sexual spores. [2]
Sexual structures are rarely observed in this genus; when present, they are in the form of dark red to nearly black apothecia ringed by a conspicuous rim of thallus tissue (the thalline margin ), sometimes with shallow scallops along the edge. Inside each fruit-body the epithecium —the tissue capping the spore layer—is reddish-brown, and the asci are club-shaped ( clavate ), each producing just two exceptionally large spores. These spores follow the Pertusaria pattern: they have walls so thick that two distinct layers are visible under a microscope and remain unpartitioned by internal cross-walls ( aseptate ). No separate flask-shaped conidiomata, which many lichens use for asexual conidia, have been found. [2]
All known species synthesise alectorialic acid, a yellow-reacting compound that can be used to help confirm identifications through thin-layer chromatography. [2]
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