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Diatoms of the United States is now known as Diatoms of North America.
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Apical axis




The long axis of the valve face of a pennate diatom, passing through the apices. Follows the midline of the valve and may be curved, as in the genus Cymbella. See Pervalvar axis and Transapical axis.


Round, F.E., Crawford, R.M. and Mann, D.G. (1990). The Diatoms. Biology and Morphology of the Genera. Cambridge University Press, Cambridge, 747 pp.