The larvae feed on a wide range of herbaceous plants, including Asteraceae, Convolvulaceae, Fabaceae, Geraniaceae, Hydrophyllaceae, Linaceae, Papaveraceae, Polygonaceae, Rosaceae, Scrophulariaceae and Violaceae species.
Among his many contributions to taxonomy are his treatments of the Medusagynaceae, Theaceae, Violaceae, and Canellaceae for the second edition of the Die Natürlichen Pflanzenfamilien of Engler & K. Prantl, the publication as editor with E. Werdermann, of ed.
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His main interest was in the Violaceae, Theaceae, and Bignoniaceae and, especially in his earlier years, in the flora of the Alps.