The genus
Siphula includes lichens with a shrubby, upright
thallus (the lichen body) that is sparsely branched and has a whitish appearance. The outer surface, or , is , meaning it consists of densely packed cells resembling plant
parenchyma (common plant tissue).
Siphula species partner with algae, a type of
green algae that supplies the lichen with energy through
photosynthesis. Inside the thallus, the
medulla (inner tissue layer) is compact and has fungal filaments (
hyphae) that are generally aligned in a longitudinal direction. No reproductive structures, such as
apothecia (spore-producing bodies) or
conidiomata (asexual spore-producing bodies), have been observed to occur in this genus. Chemically,
Siphula lichens contain various compounds including
p- and
m-
depsides,
dibenzofurans, and
chromones, such as the compound
siphulin. ==Habitat and distribution==