Environmental Engineering Reference
In-Depth Information
of a holdfast. Often in association with
Microspora assemblages. Can also be found
on soils. Chlorophyta. Plate IV.
(b) Plants larger. Cells
7 μm in diameter.
The first cross walls of each branch occur at
the origin of the branch. Pyrenoids present
..................................... 22
>
22 (21) (a) Filaments and branches tapering gradu-
ally, over two or three cells, to a fine point
.......................... Stigeoclonium
100 μm
(see also key No. 17)
(b) Filaments tapering abruptly, not gradu-
ally, with a rounded blunt end cell. ...... 23
Figure 4.6 Cladophora . General view of filaments,
showing newly formed branches.
23 (22) (a) Branches, which may be sparse in occur-
rence, usually short, sometimes consisting of
only one cell and almost rhizoidal in appear-
ance . ..................... Rhizoclonium
may be alternate or opposite, dichotomous
or even trichotomous. Cell walls are robust
and the chloroplast net-like (reticulate) and
parietal with numerous pyrenoids. Cells 50-
150 μm wide, up to ×10 long as wide. Com-
monly known as 'blanket weed' it can form
extensive, coarse-to-touch mats. Frequent in
hard or semi-hard waters, and estuarine habi-
tats, especially those enriched with sewage.
Cladophora can also produce large growths
in water treatment filtration systems such as
slow sand filters where severe problems of
filter clogging may result. Chlorophyta. Figs.
2.28 and 4.6).
Rhizoclonium forms coarse, wiry filaments
with short sometimes rhizoidal branches
although these are not always present. Cells
elongate, with robust walls, 10-40 μm wide,
2-8 times as long as they are wide. Chloro-
plast net-like with numerous pyrenoids.
Common in hard, shallow, waters where
it may be found in dense mats. Often
found with (and confused with) Cladophora.
Chlorophyta. Plate IV.
(b) Branches often longer and more robust.
Repeated branching may occur, depending
upon conditions - but they may be few and
far between. ................. Cladophora
(Not to be confused with Pithophora , which
is common in ponds but whose filaments
frequently contain dark akinetes that are
swollen and barrel-shaped. Cells 20-100 μm
wide, up to 400 μm long. Not illustrated).
Cladophora is typically well branched, but
in gently flowing waters branching may be
intermittent and difficult to find. In con-
trast, on a lake shoreline habitat subject to
choppywaveactiontheformmaybetuftedor
bush-like with many branches. Cladophora
may be free-floating or attached to a sub-
strate by means of a small holdfast. Branches
24 (5) (a) Cells with a siliceous wall . . ....... 25
To determine whether a silica wall is present,
it may be necessary to 'clean' the specimen
with a suitable oxidising or acidifying agent
(see Section 2.5.2). Some indication can be
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