Valve morphology of the different strains of Hantzschia abundans. (a–l) Light micrographs. (a–c) H. abundans MZ–BH1. (d–f) H. abundans MZ–BH2. (g–i) H. abundans MZ–BH6. (j–l) H. abundans MZ–BH7. (m) Scanning electron micrograph of H. abundans MZ–BH1, exterior of valve at valve center, showing the bent of the raphe near the central raphe endings. (n) Scanning electron micrograph of H. abundans MZ–BH7, interior of valve at valve center, showing the unilateral bent of the central raphe endings. Scale bars (a–l) = 10 µm, (m) = 5 µm, (n) = 0.5 µm.