Environmental Engineering Reference
In-Depth Information
96 (92) (a) Cells bearing long spines and form-
ing free-floating colonies of 4-16 cells
........................... Micractinium
Cells (3-7 μm diameter) more or less spher-
ical, forming small clusters or colonies, 4
being the most frequent number but can be
many more. Each cell with 1-5 fine tapering
spines, 10-35 μm long. Chloroplasts parietal
with a single pyrenoid. Occurs frequently in
the plankton of lakes, ponds and larger rivers,
especially if enriched with nutrients. Chloro-
phyta. Plate XII. Fig. 4.72.
(b) Cells without spines . .............. 97
25 μm
97 (96) (a) Cells globose to spherical forming a
tightly packed hollow sphere of up to 100
cells................................. 98
Figure 4.48 Coelastrum. Hollow colony of closely
joined, regularly arranged cells. Reproduced with per-
mission from G. Ji.
(b) Cells oval or with finger-like processes
extending outwards, more loosely arranged.
Oval cells may have thickened poles or may
be within an encasing envelope . ........ 99
slow flowing rivers. Chlorophyta. Plate XIII.
Fig. 4.48.
98 (97) (a) Up to 100 cells per colony, loosely held
together by the mother cell walls from the
previous generation . ............. Westella
99 (97) (a) Cells with finger-like or spike-like pro-
cesses extending outwards (1-4 per cell).
Cells kidney or pear-shaped and joined to
each other by a mucilaginous protrubance so
as to form a radiating colony. . . . Sorastrum
Westella cells form a free-floating colony
loosely connected by the original mother cell
walls. Cells 3-9 μm in diameter, chloroplast
parietal with or without a pyrenoid. Plank-
tonic in ponds and lakes.
Sorastrum is related to Pediastrum but the
cells form a more spherical colony of 8-64
cells. Chloroplast parietal with a pyrenoid.
The outer facing surface of the cell bears
1-4 finger- or spine-like processes 4-15 μm
long. Uncommon, found in similar locations
to Pediastrum. Chlorophyta. Plate XIII.
NB. Some authors regard Westella as syn-
onymous with Dictyosphaerium. Chloro-
phyta. Plate XII.
(b) Hollow spherical colonies of up to 64
closely joined cells arranged in a regular
sphere rather like a football . . . . Coelastrum
(b) Cells ovoid to spherical and without
finger-like processes or spines .. . ...... 100
Cells of Coelastrum are spherical, 8-
30 μm in diameter with a parietal chloro-
plast and pyrenoid. Found in the plank-
ton of eutrophic and mesotrophic lakes and
100 (99) (a) Cells (4-50 μm long) usually oval and
often having a clearly observable polar
swellingornoduleateachend.Mothercell
wall, when present, more or less entire and
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