Medulla (lichenology)

The medulla is a horizontal layer within a lichen thallus. It is a loosely arranged layer of interlaced hyphae below the upper cortex and photobiont zone, but above the lower cortex.^[1] The medulla generally has a cottony appearance. It is the widest layer of a heteromerous lichen thallus.

References

1. ^ Galloway, D.J. (1992). Flora of Australia - Lichen Glossary http://www.anbg.gov.au/glossary/webpubl/lichglos.htm