22 Siphula is a genus of lichen-forming fungi in the family Icmadophilaceae.

The widespread genus was circumscribed by the Swedish mycologist Elias Fries in 1831.

The outer surface, or cortex, is pseudoparenchymatous, meaning it consists of densely packed cells resembling plant parenchyma (common plant tissue).

[4] Inside the thallus, the medulla (inner tissue layer) is compact and has fungal filaments (hyphae) that are generally aligned in a longitudinal direction.

[4] Siphula species are found growing on peaty soils and on acid-leached bark in temperate rainforests as well as in wet alpine environments.