Description
Involucropyrenium species have a minute but robust body (thallus) that consists of tiny, overlapping squamules —scale-like lobes—which in some taxa coalesce into a thin crust. These squamules are anchored to rock or bark by a mesh of colourless to brown, root-like fungal threads (rhizoidal hyphae). The photosynthetic partner ( photobiont ) is a unicellular green alga of the chlorococcoid type. An upper cortex only 10–30 micrometres (μm) thick overlies the algal layer ; it is uneven, poorly separated from the tissue beneath, and built from small, polygonal cells 5–8 μm across. A distinct lower cortex is absent, so the hyphae merge directly into the substratum . [2]
Reproduction takes place in perithecia—flask-shaped fruiting bodies that push up between the squamules. Each perithecium is capped by an involucrellum , a dark sheath that may cover just the apex, half-wrap the wall, or surround it entirely. The perithecial wall ( exciple ) comprises elongated cells arranged parallel to the surface; it is often darkened around the ostiole—the pore through which spores exit—while the lower portion ranges from pale to blackish. Only short ostiolar threads ( periphyses ) occupy the cavity; the interascal filaments seen in many lichens are lacking. The spore sacs (asci) are club-shaped, thin-walled, non-amyloid (they do not stain blue in iodine), and contain eight colourless, single-celled ascospores arranged in two rows. The spores are broadly ellipsoidal to ovoid. [2]
No specialised asexual structures (conidiomata) have been observed, and thin-layer chromatography has yet to detect any secondary metabolites. [2]
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