Lichens in the genus
Parallopsora have a thallus—a crust-like body that consists of small, overlapping scale-like structures (). The thallus may either form as an effuse, spreading layer or take on a circular form with radiating lobes at the edges. The squamules, which are up to 2 mm wide, adhere tightly to the when young but soon become elevated and (overlapping like roof tiles). The upper surface of the thallus is typically pale green to bluish green and can be smooth () or finely hairy (). Some species in this genus may produce powdery reproductive structures called
soralia, but these are not always present. The genus lacks a , which is a fungal mat that some lichens develop around the thallus edges. The upper (the outermost layer of the thallus) is composed of irregularly arranged, thick-walled fungal filaments called
hyphae, but it does not contain crystals or a dead layer of cells known as the . The lichen's symbiotic algae are unicellular and
green, and the internal tissue (
medulla) may or may not contain lichen-specific chemicals. Unlike some lichens,
Parallopsora lacks a lower cortex, meaning the thallus is not protected on its underside. The
apothecia (fruiting bodies) are small, (without a ), and typically brown in colour. They can reach up to 1.0 mm in diameter, have a slightly convex shape, and their edges are poorly defined, often disappearing as they mature. Inside the apothecia, the
hymenium—the spore-producing layer—contains
paraphyses (sterile support filaments) and
asci (sac-like structures that contain spores). The paraphyses are straight and unbranched, while the asci are (club-shaped), containing eight simple or faintly
septate (divided) that are slender and rod-shaped ( to ). The genus does not produce any visible
conidiomata (asexual spore-producing structures). Some species of
Parallopsora produce
secondary metabolites such as
homosekikaic acid and
sekikaic acid, while others do not produce any detectable lichen substances. ==Species==