Racomitrium lanuginosum

Tortula muralis Photographed by Derek Christie near Perth, Scotland.

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This is Hedwigium ciliata var. leucophaea. It is in the Hedwigiaceae family, named after Johannes Hedwig, the father of bryology.

This is Johannes Hedwig, a Romanian doctor in the 18th century who later became a botany professor at the University of Liepzig. He is actually known as the founder of bryology, and the Hedwigiaceae family is named after him. He was the first person to clarify the life cycle of mosses.

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This is William Mitten. He was a British pharmaceutical chemist who compiled a collection of over 50,000 plant specimens, mostly mosses, in his lifetime. He was a bryologist, someone who studies mosses.