Cyphellostereum

Cyphellostereum is a genus of basidiolichens. Species produce white, somewhat cup-shaped fruit bodies on a thin film of green on soil which is the thallus. All Cyphellostereum species have nonamyloid spores and tissues, lack clamp connections, and also lack hymenial cystidia.

DNA research has shown that a common, north temperate species formerly known as Cyphellostereum laeve is not related to the type species and belongs in a quite separate order, the Hymenochaetales. It has been renamed Muscinupta laevis.

Etymology

The name Cyphellostereum combines two generic names: Cyphella in reference to the inverted cupulate form (like the genus Cyphella); and Stereum, in reference to the stipitate fan-shape or bracket shape (as in species of Stereum).

Evolution and morphology

Multilocus phylogenetic trees recover Cyphellostereum as a monophyletic, basal branch that is sister to all other genera in the Dictyonema clade. Occupying this early-diverging spot, the genus retains the simplest thallus: a bluish, crust-like weave of cyanobacterial filaments (trichomes) sheathed by the fungus, with no layered cortex or medulla that would distinguish an upper or lower surface. Its reproductive structures are tiny, cup-shaped cyphelloid fruiting bodies (basidiocarps) that sit on the thallus rather than being swallowed by it; the hyphae that build these cups differ markedly from the slender hyphae that merely clothe the photobiont threads. The fungal sheath is made of irregular, cylindrical cells full of air-gaps and it entirely lacks the tubular haustoria and "jigsaw-puzzle" cell walls that later genera use to tap nutrients from the cyanobacteria.