Environmental Engineering Reference
In-Depth Information
central terminals hooked/bent in opposite
direction..............
Neidium binodis
opposite directions. Cells vary in size: 15-
200 μm long, 4-30 μm wide - depending
on species. Widespread in nutrient-poor
or mildly acidic waters. Bacillariophyta.
Plate XXVI.
Neidium binodis
has two chloroplasts
(other species of
Neidium
have four) each
containing a pyrenoid. Cells 15-120 μm
long, 4-30 μm wide, linear to lanceo-
late with widely rostrate ends. The valve
surface has fine striae which may be
interrupted near to the valve margin.
Central ends of raphe bent in opposite
directions. A widespread genus found in
oligo- to mesotrophic waters. Bacillario-
phyta. Plate XXVI.
(b) Less than four chloroplasts per cell
..................................
196
196
(195) (a) Two plate-like chloroplasts, one either
side of long axis, sometimes with lobed
margins. Stauros (see Glossary) present
..................................
197
(b) Cellsnotasabove..............
198
(b) Two chloroplasts typically present,
one either side of the long axis. Central
raphe terminals straight or bent the same
way. Clear marginal lines present. Cells
withwiderostrateapices.......
Caloneis
197
(196) (a) Central area of valve wider, with striae
missing, and the clear area reaching nearly
completely from side to side forming
the stauros. Cells rhomboidal to linear-
lanceolate . .................
Stauroneis
Caloneis
cells (60-125 μm long, 25-
30 μm wide) are elliptical to fusiform
with rounded to rostrate or capitate ends.
There is either a single plate-like chloro-
plast or two lying either side of the
axial line. The valve face bears line.
striae which are interrupted by a line just
inside the valve margin. The raphe ends
are either straight or both bent to the
same side. Frequent on rocks and stones
in streams and amongst mosses, some-
times in alkaline waters. Bacillariphyta.
Plate XXVI.
The valves of
Stauroneis
are lanceolate
to elliptical with rounded or rostrate ends.
The valve surface has parallel to slightly
radiate striae with a marked clear area
or stauros in the central region which
extends to the valve margin. Cells (8-
160 μm long, 3-20 μm wide) contain two
chloroplasts, one lying each side of the
apical axis, with one to many pyrenoids.
A widespread genus - common on damp
rocks and amongst mosses, with many
species occurring in more oligotrophic
waters including lakes. Bacillariophyta.
Plate XXVI.
195
(193) (a) Four chloroplasts per cell. . .
Neidium
(b) Valves widely lanceolate, clear central
area not quite reaching the cell margins. A
prominent stigma is present at one side of
the central area . ..............
Luticola
Neidium
cells typically have four chloro-
plasts (each with pyrenoid) per cell
although
N. binodis
(see key No 194) has
two H-shaped chloroplasts. The valves are
linear to lanceolate with the cell apices
broadly rostrate. The valve is ornamented
withrowsofpunctaewhichareinterrupted
by a series of small gaps near to the mar-
gin.Thereisaraphewhoseendsarebentin
Valves linear, elliptical or lanceolate with
rounded to slightly capitate apices. Valve
surface with radiate, punctate, striae. Wide
central area which does not extend to
the valve edge. Raphe straight. Cells
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