Cladonia macilenta

Cladonia macilenta or the lipstick cup lichen is a species of cup lichen in the family Cladoniaceae.

The species is red listed in Iceland as an endangered species (EN). While it is found in various regions of the UK, it is considered potentially threatened in parts of the lowlands due to habitat loss.

Verrucaster lichenicola, described by Friedrich Tobler in 1913, was proposed to be a fungus with waxy pycnidia and hyaline conidia lacking septa. It was, however, a little-known taxon, as the type specimen was lost and not collected again. The rediscovery of the type material more than a century later revealed that what Tobler thought to be a lichenicolous fungus was instead pycnidia of Cladonia macilenta, and thus the two taxa are placed in synonymy.

Description
Cladonia macilenta is small- to medium-sized amongst other Cladonia species and notably lacks cups even at maturity. Typically, it is found in open or well-lit wooded areas and heathlands growing on strongly acidic wood and soil. It is often mistaken for Cladonia polydactyla, because some morphs of that species can lack cups, particularly when pollution-stressed, shaded, or juvenile. but C. macilenta can be differentiated coloration (C. macilenta is typically white or grey, while C. polydactyla is typically blue-grey) or by the reproductive structures (soredia) which are granular in C. polydactyla and more mealy (farinose) in C. macilenta.