Thalloidima physaroides (Opiz) Kistenich, Timdal, Bendiksby & S.Ekman

Thalloidima physaroides is similar to T. sedifolium, from which it differs in the habitus of its thallus, presence of pseudcyphellae, mostly colourless hypothecium and inner part of exciple. However, T. physaroides is often sterile and the pseudcyphellae are not well-visible in strongly pruinose specimens. In such cases, the two species can be distinguished based on the thickness of medullary hyphae walls, which are much thicker in T. physaroides (Timdal 1992).

It grows on slightly calcareous soil at well-lit stands, usually of early successional stages, typically on sandy substrates or in steppic communities. It is often associated with cyanolichens when young, later with mossy cushions. It occurs from lowlands to mountains but is more common in warmer areas. It prefers continental areas.

This lichen was described by P. M. Opiz in 1856 as Lecidea physaroides from sandstones between Libeň and Prosek in Prague („ober Lieben gegen Prosik“; Opiz 1856), which probably refers to Cenomanian sandstones in the Prosecké skály Nature Reserve, largely ruderalized and overgrown by forest nowadays. The occurrence of T. physaroides has not been confirmed there recently. In the Czech Republic, it is a very rare lichen of xerothermic areas, mainly endangered by succession of suitable habitats. It has recently only been found in Central Bohemia, on diabase and limestone outcrops in Český kras (the Bohemian Karst) and the Prokopské údolí valley in Prague. It also occurs on calcareous sandstones in the Mělník region. Its centre of distribution lies in central and southern Europe.

Literature: Opiz P. M. (1856): Lichenologische Nachträge zu meinem Seznam rostlin Květeny české. – Lotos 6: 19–22, 41–45 & 155–158. Timdal E. (1992): A monograph of the genus Toninia (Lecideaceae, Ascomycetes). – Opera Botanica 110: 1–137. Malíček J. & Palice Z. (2009): Tři pozoruhodné lišejníky na diabasech v Praze a v Českém krasu. – Fragmenta Ioannea Collecta 11: 21–33.

Ascomycota → Lecanoromycetes → Lecanorales → Ramalinaceae → Thalloidima