Environmental Engineering Reference
In-Depth Information
50 μm
50 μm
50 μm
10 μm
Figure 4.13
Spirogyra
. Top: Species with multiple
(about 6) spiral chloroplasts and simple cross walls. The
chloroplasts have numerous pyrenoids (small dots). Bot-
tom: Species with two chloroplasts and complex (repli-
cate) cross walls (arrows).
Figure 4.12
Diatoma
.Top:Star-shapedpatternofcells
at edge of planktonic colony. Bottom: Single cell, show-
ing transverse costae. Reproduced with permission from
M. Capstick. Acid digest, lake sediment sample.
material, is in the centre of the cell. Cells
are 10-160 μm in diameter, up to 590 μm
long. Filaments fragment easily at the cross
walls, each fragment growing into a new
filament. Sexual reproduction in
Spirogyra
involves conjugation between cells of differ-
ent filaments and results in the production
of a resistant zygote. Common and widely
distributed in shallow ponds and ditches,
mostly stagnant waters which are neutral to
slightly acid although
S. crassa
is confined
to hard waters.
Spirogyra
can form dense
green masses and can grow in large enough
amounts in shallow open water treatment fil-
ters to cause blockage. Nearly 400 species
have been listed worldwide including com-
moner species such as
S. condensata
,
S. lon-
gata
,
S. neglecta
and
S. tenuissima
. Chloro-
phyta. Plate V. Fig. 4.13.
(b) Chloroplasts not in the form of a spiral
band . ................................
31
31
(30) (a) Filaments are unbranched with the cells
embedded in a prominent wide mucilagi-
nous hyaline cylindrical envelope or sheath.
Cellsareshortcylinderswithwidelyrounded
ends.. ........................
Geminella
Cellsare5-25μmwide,uptotwiceaslongas
they are wide, and are surrounded by a thick
mucilage sheath. Cells often occur in pairs
along the filament. The chloroplast is a pari-
etal plate, roughly saddle-shaped and located
near the central region of the cell. A pyrenoid
is usually present. Reproduction is by frag-
mentation of the filament. Occurs in shallow,
often slightly acidic, waters where desmids
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