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).[1] While it is found in various regions of the UK, it is considered potentially threatened in parts of the lowlands due to habitat loss.[2]
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.
Cladonia macilenta is small- to medium-sized amongst other Cladonia species and notably lacks cups even at maturity.[2] 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,[2] 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.[2]