The morphology and integration of valves and bands in Navicula mutica var. mutica (Bacillariophyceae) [Algae]

N. mutica (Kuetz) var. mutica was isolated from the air, cloned on agar, cultured in soil-water bottles, and studied with transmission and scanning electron microscopy. The frustules were lanceolate to ovoid with rounded apices, with the apical axis 8.5 plus or minus 3.2 mu m and the transapical axis 3.6 plus or minus 0.6 mu m. Striae were composed of two or three puncta, and the mantle bore a single row of puncta aligned with the striae. The ends of the raphe turned away from an isolated punctum in the central area of the valve. The mantle puncta and one or two of the valve-face puncta in each stria opened into a series of transapical grooves in the interior of the valve, the grooves contributing to the appearance of striae in the light microscope. The projections of the undulate margin are perhaps positioned between the transapical grooves and along the longitudinal groove between the dentiform structures formed by the intersection of the double-grooved system. The girdle bands each had two (occasionally three) rows of pores. The pleurae margins were straight and not undulate.