FIGURES 67–71 in Ultrastructure of four Surirella taxa (Bacillariophyceae) from Qinghai Province, northwest China, with reference to the characteristics of portulae

FIGURES 67–71. Surirella lacrimula, SEM, external view. 67.A complete valve showing the relatively flat valve surface and inconspicuous costa-stria bundles (CSBs). 68, 69. Details of the apices, from Fig. 67. 70, 71. Details of the middle section of the valve, from Fig. 67. Note that over-fibula costae (OFCs) are difficult to distinguish. Scale bars = 5 μm (Fig. 67), 1 μm (Figs 68–71).