1. Flowering shoot with erect catkins with male (a, b) flowers above and females (c, d, e) toward their base. One to three flowers are located in each female inflorescence (cupule, involucre). - 2. Branchlet with ripe fruits. The cupules are prickly and splitting into four valves. - 3. Seed (»chestnut«) from the middle of a cupule as seen from two aspects (a, b), and one, taken from lateral position (c). - 4. Winter-branchlets are angular and densely set by lenticels. After Hempel & Wilhelm, 1889. Photos and explanations from the book: Zelimir Borzan. "Tree and Shrub Names in Latin, Croatian, English, and German, with synonyms", University of Zagreb, 2001.