01521nas a2200145   4500008004100000245004900041210004900090300000900139490000700148520105900155100002001214700002401234700001701258856010001275       2007                        eng d00aExotische muurvarens in België en Nederland0 aExotische muurvarens in België en Nederland  a1-160 v923 aExotic mural ferns in Belgium and the Netherlands. In recent years an increasing number of exotic mural ferns have been recorded in urban areas of Belgium and the Netherlands. Without exception, these plants have escaped from cultivated individuals of which tender taxa bave profited by microclimate and environmental conditions present in larger cities ('heat islands'). The present paper deals with recent records of Adiantum capillus-veneris, A. diaphanum and A. raddianum, Cyrtominm falcatum and C, fortunei, Dryopteris cycadina, Polystichum tsus-simense, Pteris cretica s.l. and P. multiflda. Most of these taxa are (very) frost-sensitive and their appearance may be temporary (Cyrtomium falcatum in the Netherlands excepted). Identification keys, photographs, original line drawings and herbarium scans are presented here for most of the escaped species to facilitate identification. In addition, distributional records and ecological comments are provided and reasons why the sudden increase in occurrence of exotic ferns in urban areas discussed.1 aVerloove, Filip1 avan de Ham, Raymond1 aDenters, Ton  uhttps://alienplantsbelgium.myspecies.info/content/exotische-muurvarens-belgi%C3%AB-en-nederland