''Rhizoplaca chrysoleuca'' (orange rim lichen, rock-posy lichen, rockbright) is a pale yellowish-green to gray-green umbilicatefoiliose
lichen
A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship. /ref> It was first species description, described in 1791 by English botanist Sir James Edward Smith as ''Lichen chrysoleucus''; Friedrich Wilhelm Zopf transferred it to the genus ''
Rhizoplaca
''Rhizoplaca'' is a genus of lichenized fungi in the family Lecanoraceae. Members of the genus are commonly called rimmed navel lichens because of their umbilicate growth form and lecanorine (rimmed with thallus-like tissue)apothecia
An a ...
'' in 1905.
The single-leaf ( monophyllous) umbilicate thallus can be 2–3.5 cm in width, with deep lobes. The
thallus
Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms wer ...
is relatively thick and lumpy with warts and lobules. The fruiting structures ( apothecia have lightly
pruinose Pruinescence , or pruinosity, is a "frosted" or dusty-looking coating on top of a surface. It may also be called a pruina (plural: ''pruinae''), from the Latin word for hoarfrost. The adjectival form is pruinose .
Entomology
In insects, a "blo ...
, burnt-orange to tan discs rimmed, with a contrasting rim of pale greenish thallus-like tissue making them easy to identify. Apothecia are 0.8–2.5 mm diameter, and often numerous and crowded into each other.
It grows in
Eurasia
Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago a ...
and western
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
. In the Sonoran Desert region it grows at elevations from . It prefers
siliceous rock
Siliceous rocks are sedimentary rocks that have silica (SiO2) as the principal constituent. The most common siliceous rock is chert; other types include diatomite. They commonly form from silica-secreting organisms such as radiolarians, diatoms, or ...
,
granite
Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...
,
schist
Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes o ...
,
quartz
Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...
,
mica
Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...
, and
basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
, but is also found on
sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates) ...
and less commonly on
calcareous rock
Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.
In zoology
''Calcareous'' is used as an adje ...
. It grows from the high desert to the alpine zone. It is often
nitrophilous Nitrophily is a botanical term that indicates a preference of certain plant species for a habitat rich in nitrate. This term was first introduced by George Fuller during the 1930s. The word is a contraction of the Greek words νἰτρον (nitron ...
, preferring dropping areas under bird perches. It is common on rock in inland arid mountain and desert habitats in
California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
.Field Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014,
Lichen spot test
A spot test in lichenology is a spot analysis used to help identify lichens. It is performed by placing a drop of a chemical on different parts of the lichen and noting the colour change (or lack thereof) associated with application of the chemical ...
s are K+ yellow or K−, KC+ yellow-orange, C−, and P− on the cortex, and K−, KC+ red or KC−, C−, and P+ yellow or P− on the medulla.