Wikipedia
Psilon
A ' Psilon' is a unit of length that is equal to 44 manly strides or, less precisely, 0.025 miles (a quarter of a tenth of a mile) or 40 meters. The Psilon is best known as the official unit of measurement during the censusing of plants in the genus Silene (see Silene) in a metapopulation surrounding Mountain Lake Biological Station in Giles County, Virginia.
Etymology: Derived from the Latin Silene.