THE ULTRASTRUCTURE AND MORPHOLOGICAL VARIABILITY OF THE FRUSTULE OF <i>STEPHANODISCUS INVISITATUS</i> HOHN AND HELLERMAN¹

Abstract

SUMMARY Stephanodscus invisitatus Hohn and Hellerman, studied by means of light, transmission, and scanning electron microscopy, shows a range of frustule diameters from 6.4 to 13.3 μ. Variation in valve ornamentation can be correlated with specimen diameter. The striae number ranges from 16 to 20 in 10 μ. Various processes difficult to observe by light microscopy alone are described which arise from the inside and outside of the frustules. 2