Mosses of the island of Griend (prov. Friesland) The island of Griend came into existence in the Middle Ages. Nowadays it is a small, low, flat sandy island located in the western Waddensea about halfway between the port of Harlingen and the West Frisian barrier island of Terschelling, Province of Fryslân. It is famous for its dense breeding colonies of sea birds, in particular those of the Common Black-headed Gull and three Tern species, among which the Sandwich Tern. The early history of the bryoflora of the island is not known. From the second half of the 19th century to the 1970s bryophytes were probably absent from the island vegetation due to a combination of factors, e.g. a limited number of suitable habitats (salt marshes and areas under constant thread of covering by wind-blown sand are unsuitable habitats), a low diversity in habitats due the island's level surface, occasional high tidal flooding throughout the year, and a dense vegetation of grasses due to enrichment with nutrients from the breeding colonies. To protect the island from thread of being swallowed by the sea, a few sand dykes have been constructed in 1973, 1985, and 1988. A few years after the construction of the last sand dyke was completed, the first moss species have been reported for the island. In 2002 and 2003, the authors of this paper made a complete inventory of the bryoflora of Griend, which has resulted in a list of nineteen moss species, of which 13 are new for the island. The occurrence of mosses is restricted to the man made sand dykes. The most spectacular find is Eurhynchium speciosum (Brid.) Jur., which is rare in the Dutch Waddensea area. In combination with other recent records of E. speciosum in this area, the recent find on Griend suggests that the species is currently increasing in the Dutch Waddensea area. Inleiding Griend is een klein eiland in de westelijke Waddenzee en ligt ongeveer halverwege tussen Harlingen en Terschelling. Het eiland is beroemd vanwege de vele wadvogels die bij hoogwater op en nabij het eiland rusten en vanwege de dichtbevolkte broedkolonies van, onder andere, de Kokmeeuw, de Grote stern, de Noordse stern en de Visdief. Griend is van oorsprong een Middeleeuws eiland, dat in de loop van de geschie-denis steeds kleiner geworden is. Het eiland is laag en bestaat uit een lage kwelder met daaromheen een aantal zanddijken van verschillende ouderdom. Boven de hoogwaterlijn is het eiland, inclusief de zanddijken, tegenwoordig ongeveer 60 ha groot. Over de vroegste geschiedenis van de mosflora van Griend is helaas niets bekend, maar vanuit moskundig