marsh lousewortn. a crimson-flowered plant of the family Scrophulariaceae, Pedicularis palustre, found in marshes and damp meadows in Europe (also called red rattle or marsh red rattle).
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1762 W. HudsonFlora Anglica 236Pedicularis..palustris... Marsh Louse-wort.
1989 Where to go for Wildlife (BBONT) 130 There are many colourful flowers to interest the visitor [to Bullingdon Bog], such as marsh helleborine..marsh lousewort..and the handsome butterwort.