Protracted Tarpaper Lichen

The lichen genus Callome is characterised by its small, foliose (leaf-like) thallus, typically ranging from 1 to 3 cm in diameter, though it can sometimes reach up to 5 cm. The thallus is rounded or irregular in shape, with deep lobes and extensive branching. It is loosely attached to its substrate and partly ascends, giving it a delicate and fragile appearance. When wet, the thallus does not swell, and the central part may degrade over time, leading to very irregular shapes. The lobes are narrow, about 1 to 1.5 mm wide, and are often fan-shaped, twisted, and nodular. These lobes are convex and can become almost cylindrical, with repeated branching. Unlike many other lichens, Callome lacks a cortex (a protective outer layer), and its thallus is composed of a uniform layer of hyphal cells mixed with chains of photobiont cells, which are responsible for photosynthesis. The upper surface is a dark olive-green to brown-black colour and has a matt finish. It is smooth or may have fine, longitudinal striations but does not have a fuzzy or hairy texture. When moist, the surface can appear slightly swollen and semi-transparent. Reproductive structures called conidiomata are commonly found within the thallus and are typically immersed in the surface. …

Callome multipartita is known to occur in Northern Africa, Europe, and North America, where it grows on rocks.

== References ==

Endococcus pseudocarpus is a lichenicolous fungus that is known to use Calloma as a host lichen.