Christine Keller

Hydropunctaria maura, still often called by the older name Verrucaria maura and commonly known as tar lichen, is a species of saxicolous (rock-dwelling), crustose lichen belonging to the family Verrucariaceae. A perennial species that does not experience seasonal variations, it is the type species of the genus Hydropunctaria. The medulla is a black basal layer that forms columns (Latin: punctae) to the upper surface and isolates the algae into pockets near the upper surface. The black band formed by H. maura can often be seen at a distance as a marker of the high water point.

Hydropunctaria rheitrophila is a widely distributed species of crustose lichen in the family Verrucariaceae. It grows on rocks in aquatic environments, typically in streams and rivers where it colonizes silica-containing substrates that are regularly submerged or wetted. The lichen forms a thin to thick crust-like body (thallus) that ranges in colour from pale brownish green to dark green, often dotted with black spots. It is widely distributed throughout the Northern Hemisphere, particularly in Europe, North America, and Asia, with some occurrences in the Southern Hemisphere including New

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