THE MORPHOLOGY AND INTEGRATION OF VALVES AND BANDS IN NAVICULA MUTICA VAR. MUTICA (BACILLARIOPHYCEAE)1

Abstract

ABSTRACT Navicula mutica (Kütz.) var. mutica was isolated from the air, cloned on agar, cultured in soil‐water bottle, and studied with transmission and scanning electron micros‐ropy. The frustules were lanceolate to ovoid with rounded apices, with the apical axis 8.5 ± 3.2 μ and the trans‐apical and the transapical axis 3.6 ± 0.6 μm. 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 punctual 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 interior of the mantle also possessed a pair of longitudinal grooves, discontinuous at the apices of the valves. An undulate advalvar margin of the valvocopula likely articulates along the interior longitudinal groove of the mantle. 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.