Cladonia borealis
A Red Pixie Cup, which is a probably very over looked member of the Cladonia coccifera aggregate. Most similar to Cladonia coccifera s. str., with wide flaring cups with corticate granules inside, but in contrast but has a smooth cortex on the base of the podetia, where it is at most broken into plates. The cortex on Cladonia coccifera s. str. becomes areolate and breaks down to become irregularly granular above. Very under recorded but probably frequent in the uplands in the north but rare to the south.
Similar to Cladonia coccifera s. str., but the surface of podetia (which are frequently fertile) are uniformly smooth to shallowly areolate-corticate, without granules or minute squamules, with flat corticated cracked plates outside but flattened corticate granules inside the cup. Thallus C–, K–, KC+ yellow, Pd–, UV– (usnic and barbatic acids).
Little recorded and overlooked in Britain and Ireland, but actually quite distinctive in the combination of smooth podetia, wide cups and the corticate granules confined to inside the wide splayed out cups. Compare also with Cladonia diversa.
On peaty soil, mostly in upland heaths, but also in richer lowland heaths.
So under recorded that the distribution is not clear, but probable frequent in the Scottish Highlands but much rare beyond.
Britain: Notable and Data Deficient
Pino-Bodas, R., Sanderson, N., Cannon, P., Aptroot, A., Coppins, B., Orange, A. & Simkin, J. (2021). Lecanorales: Cladoniaceae, including the genera Cladonia, Pilophorus and Pycnothelia. Revisions of British and Irish Lichens 19: 1-45. Link
Text by N A Sanderson, based Pino-Bodas et al (2021)