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Trichomanes (bristle-ferns; family Hymenophyllaceae) A genus of filmy ferns that differs from Hymenophyllum in the cylindrical or bell-shaped indusium surrounding each marginal, gradate sorus, and in its filamentous (not flat as in Hymenophyllum) gametophytes. The tip of the soral placenta eventually projects as a bristle from the indusium. In the wide sense there are some 330 species, but some authors divide the genus into many smaller genera. The plants occur throughout most tropical zones, with a few outliers in mild, moist, temperate zones (e.g. T. radicans, Killarney bristlefern, found in western parts of the British Isles).