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Diatoms of the United States is now known as Diatoms of North America.
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Glossary terms starting with "e"



Having notably more length than width. Having a long and slender shape.



Native, or limited to a specific geographic area.



Algae which grow within the subsurface of sediments, clays, and silt.


An organism that lives inside another, benefitting both individuals. For example, endosymbiotic cyanobacteria often inhabit living cells of the genus Epithemia.



Algae which grow on the surface of rock or stone.



Algae which grow on the surface of sediments, clays, and silt, i.e., residing at the water/sediment interface.

Epiphytic - periphyton

The growth habit of organisms that live on the surfaces of plants or other algae.


The growth habit of living attached to sand grains, or moving through sand.



The larger theca of the frustule. The epitheca overlaps the hypotheca. A theca is composed of a valve and its associated cingulum. From Greek, theca means sheath or case (plural is thecae), so epitheca means outer sheath.


External tube

An extension of a fultoportula on the valve face having the shape of a tube. Typically it is a simple tube, but may be variously shaped.