Roccella presents a
fruticose (shrub-like),
thallus that is either erect or (hanging) with sparse branching. The main and terminal , varying in shape from flattened to rounded (), typically measure 2 to 5 mm (up to 10 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 (powdery) or lacking pruina (epruinose).
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 (the inner layer) is loosely structured above, having a byssoid (fibrous) or chalky texture, and below it becomes (tightly packed cells) near the basal plate (
holdfast) area, often showing a (yellowish) 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 (spore-producing structures) 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 (the outer layer of the ascomata) 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 (upper layer of the ascomata) is about 40 to 50 μm high, brown, with intertwined (supporting structures in the hymenium) that are sparsely branched. The
hymenium (spore-bearing layer) itself is 70 to 90 μm high. Paraphysoids within the hymenium are sparsely branched,
hyaline (translucent), and measure 1 to 2 μm in diameter. The (layer beneath the hymenium) is distinct, dark brown, , and does not extend into the medulla. The
asci (spore-bearing cells) are (club-shaped), measuring 60 to 85 by 12 to 14 μm. are (spindle-shaped), curved, smooth, contains three
septa (internal partitions), and are hyaline. (asexual reproductive structures) are
pycnidial (flask-shaped), solitary, immersed in the thallus, and black, measuring about 0.1 mm in diameter. The (asexual spores) are (thread-like), 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==