Unicellular or uniseriate trichomes with helical outer wall bands were found in several taxa of Rosaceae, Betulaceae, and Rubiaceae during a survey of cleared and stained leaves of 93 species in 86 genera of 52 families. Outer wall bands were most common in Rosaceae, especially Rubus. Previously, only bands on the inner wall of trichomes had been described. Trichomes with outer wall bands may provide excellent material for basic cell wall studies, and in certain families they may be a useful taxonomic character.