. Synopsis of the naviculoid diatoms. Presented to the R. Swedish Academy of Sciences May 10, 1893. Diatoms. KONGL. SV. VET. AKADBMIENS HANDLINGAE. BAND 27. N:0 3. 125 Subgenus Oxyamphora. Frustule usually broadly elliptical, with truncate ends and complex connecting zone. Valves lunate, acute. Median line approximate to the ventral margin. Central nodule transversely dilated to a stauros or not. Axial and central areas usually indistinct. No longitudinal lines or keels on the dorsal side of the valve. Structure of the dorsal side: usually fine puncta, arranged in parallel, or slightly radiate
. Synopsis of the naviculoid diatoms. Presented to the R. Swedish Academy of Sciences May 10, 1893. Diatoms. KONGL. SV. VET. AKADBMIENS HANDLINGAE. BAND 27. N:0 3. 125 Subgenus Oxyamphora. Frustule usually broadly elliptical, with truncate ends and complex connecting zone. Valves lunate, acute. Median line approximate to the ventral margin. Central nodule transversely dilated to a stauros or not. Axial and central areas usually indistinct. No longitudinal lines or keels on the dorsal side of the valve. Structure of the dorsal side: usually fine puncta, arranged in parallel, or slightly radiate, transverse striae, and in undulating, longitudinal lines. Ventral side with, usually, much closer strise than the dorsal A. hyalina with cell-contents, frustule in zonal view, in state of division, and in valvular view; 600 times magnified. A. ostrearia with cell-contents; 600 times magnified. Cell-contents. 1 have examined living specimens of A. hyalina, A. In A. hyalina there is, along the ventral side of the connecting zone, a the extremities of which are deeply indented and at the ends of which a single elseoplast constantly occurs. On the dorsal side of the plate and on its centre the nucleus occurs enclosed in a plasma-mass, from which radiate fine threads towards the wall of the frustule. On divid- ing, the plate and terminal elseoplasts are longitudinally cloven. If the living frustule be stained with methylene-blue, numerous, intensely coloured granules make their appearance in the primordial stratum of the plasma. A. ostrearia has two chromatophore-plates, one along the dorsal wall of the connecting zone. Both are deeply constricted in the middlej A. quadrata has instead of chromatophore-plates a large number of small, rounded discs, gathered below the central plasma-mass and at the extremities. It is thus, as to its cell-contents, a coccochromatic diatom. This subgenus comprises a number of forms with or without stauros, which in other respects are too close
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectdiatoms, bookyear1894
