Valve morphology of the strain Hantzschia attractiva MZ–BH11. (a–d) Light micrographs of the natural population. (e–i) Light micrographs of monoculture. (j) Scanning electron micrographs, interior of valve. (k) Scanning electron micrograph, showing the raphe keel. (l) Scanning electron micrograph, interior of valve at valve center, showing the bent of the raphe near the central raphe endings. Scale bars (a–j) = 10 µm, (k–l) = 1 µm.