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Webster 1913 Edition


Pleurosigma


Pleuˊro-sig′ma

,
Noun.
[NL. See
Pleuro-
, and
Sigma
.]
(Bot.)
A genus of diatoms of elongated elliptical shape, but having the sides slightly curved in the form of a letter
S
.
Pleurosigma angulatum
has very fine striations, and is a favorite object for testing the high powers of microscopes.