Roccella (lichen)


Roccella is a genus of 23 species of lichens in the family Roccellaceae. The genus was circumscribed by Swiss botanist Augustin Pyramus de Candolle in 1805, with Roccella fuciformis as the type species.

Description

Roccella presents a fruticose, thallus that is either erect or with sparse branching. The main and terminal, varying in shape from flattened to rounded, typically measure 2 to 5 mm in thickness and 5 to 15 cm in length. These branches has colours ranging from creamy white-greyish to greyish-brown and have surfaces that are either smooth or wrinkled, with some being sparsely or lacking pruina. Soredia, reproductive propagules for asexual reproduction, are present in many species within the genus.
The of Roccella lichens is made of hyphae that are arranged in an manner and are about 40 to 70 μm thick. The medulla is loosely structured above, having a byssoid or chalky texture, and below it becomes near the basal plate area, often showing a brown colouration. These lichens primarily associate with the photobiont Trentepohlia, with no secondary present. They attach to surfaces using holdfasts, including a hypomedulla which usually appears brown to dark brown, sometimes with a yellowish tinge.
The ascomata of Roccella are in the form of apothecia, lateral, and circular in outline. They can be either immersed in the thallus or sessile with a constricted base and can reach up to 2.5 mm in diameter. The of the apothecia is exposed, white, and features a, pruinose layer. The initially contains algae and a cortex, but over time, the algae may be displaced, and the cortex eroded. The forms a thin and is sometimes inconspicuous.
The is about 40 to 50 μm high, brown, with intertwined that are sparsely branched. The hymenium itself is 70 to 90 μm high. Paraphysoids within the hymenium are sparsely branched, hyaline, and measure 1 to 2 μm in diameter. The is distinct, dark brown,, and does not extend into the medulla. The asci are, measuring 60 to 85 by 12 to 14 μm. are, curved, smooth, contains three septa, and are hyaline.
are pycnidial, solitary, immersed in the thallus, and black, measuring about 0.1 mm in diameter. The are, curved, measuring 16 to 21 by less than 1 μm. In terms of chemistry, Roccella lichens contain orcinol and β-orcinol depsides, as well as aliphatic acids. Roccella lichens grow on rock or on bark.

Species