Asplenium ruta-muraria is a species of fern commonly known as wall-rue. In Germany

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

, it is known as Mauerraute or Mauerstreifenfarn. It is a very small epipetric species, growing exclusively on limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

 and other calcareous rocks. It is native to both Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 and eastern North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

. In Europe, it commonly invades masonry and is a common species, while in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, it is more difficult to find, favoring pockets in very well-weathered and rather dry limestone outcrops.