Paralecanographa is an unusual lichen genus because its single species, P. grumulosa, begins life as a lichen-dweller rather than an independent thallus. The fungus first infiltrates coastal crustose lichens such as Roccella or Dirina, drawing on their resources; as it proliferates it gradually overruns the host and builds a thin, crust-like body of its own, leaving the original thallus distorted and chemically altered. Infected hosts show a marked rise in gyrophoric acid and a corresponding drop in erythrin, while their surface often becomes wart-like. Sterile cushions formerly described as Ingaderia troglodytica are now recognised as early, fruit-body-less stages of the same organism.[1]
The mature lichen forms fruit bodies that range from fine, ink-line fissures (lirellae) to minute rounded discs, each slightly pinched at the base. Because the margin is composed solely of fungal tissue, there is no true continuation of the thallus around the rim; instead the exposed disc carries a dusting of fine white crystals known as pruina. Beneath this pruina the proper rim (excipulum) is conspicuously dark brown and rather carbonised, whereas the tissue immediately below the hymenium remains sealed off towards the substrate. When treated with potassium iodide the hymenial gel turns crimson, a diagnostic reaction within the order.[1]
Inside the hymenium lie slender, two-walled asci surrounded by a mesh of colourless, branching paraphysoids. Each ascus releases eight colourless, ellipsoid to spindle-shaped ascospores divided by three (occasionally up to five) transverse walls; every spore is wrapped in a gelatinous envelope, or "halo", that swells when moisture fluctuates and aids dispersal. Simple flask-shaped pycnidia are often immersed between the fruit bodies and exude curved, thread-like conidia that provide an additional means of reproduction.[1]
