Pseudocyphellae (singular ''pseudocyphella'') are structures in

lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...

s that appear as tiny pores on the outer surface (the

cortex Cortex or cortical may refer to: Biology * Cortex (anatomy), the outermost layer of an organ ** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain'' *** Motor cortex, the regions of the cerebral cortex i ...

) of the lichen. They are caused when there is a break in the cortex of the lichen, and the medullary

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...

e extend to the surface. Pseudocyphellae are the same colour as the medulla of the lichen, which is generally white, but can be yellow in some species of '' Pseudocyphellaria'' and in ''

Bryoria fremontii ''Bryoria fremontii'' is a dark brown, horsehair lichen that grows hanging from trees in western North America, and northern Europe and Asia. It grows abundantly in some areas, and is an important traditional food for a few First Nations in Nor ...

''. The presence/absence, abundance, colour, and shape of pseudocyphellae can all be diagnostic features used to identify different species. They facilitate

gas exchange Gas exchange is the physical process by which gases move passively by diffusion across a surface. For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liquid, a gas-permeable membrane, or a b ...

through the surface of the lichen, and may provide an adaptive advantage in

temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...

environments. Cetrelia_cetrarioides-1

References

*Brodo, I. M., S. D. Sharnoff, and S. Sharnoff. 2001. Lichens of North America. Yale University Press: New Haven. {{reflist Lichens Fungal morphology and anatomy