Environmental Engineering Reference
In-Depth Information
38 (37) (a) Chloroplast reticulate (see Glossary) 39
(b) Chloroplastnotreticulate........... 41
39 (38) (a) Cell walls thick, typically lamellate,
made up of two overlapping halves which
can break into H-pieces. End cells usu-
ally have H-shaped terminations. Pyrenoids
absent....................... Microspora
Microspora forms unbranched filaments,
sometimes with a holdfast substratum attach-
ment. Chloroplast is reticulate, not very well
defined, and pyrenoids are absent. Storage
product starch. Cells 5-30 μm in diameter
and one to three times as long as wide. Com-
mon but not usually abundant in small fresh-
water bodies. Some species occur in more
acid waters, for example, bogs or even acid-
mine drainage. More frequent at cooler times
of the year. The morphological characteris-
tics of this genus can vary considerably with
environmental conditions, making it diffi-
cult sometimes to separate different species.
Chlorophyta. Plate V.
50 μm
Figure 4.17 Oedogonium. The central cell (cap cell)
has residual cell wall material, seen as transverse lines
(arrow).
wide. The chloroplast is parietal and net-
like with several pyrenoids. Oogamous sex-
ual reproduction occurs with large female
oogonia and a dwarf male growing close
by, producing a thick-walled zygote. Over
200 species have been described and fur-
ther identification is impossible without the
reproductive structures being present. Abun-
dant in still or gently moving waters where
they may form dense free-floating, attached
or tangled mats. Chlorophyta. Fig. 4.17.
(b) Cell wall not thick and lamellate and
notcomposedofH-pieces.Pyrenoidspresent
..................................... 40
40 (39) (a) Cellscylindricalorslightlyswollen,with
robust walls. Cells 20-80 μm wide, 5-15
timesaslongaswide......... Cladophora
(see also key No. 23)
(b) Cells cylindrical, sometimes slightly
swollen at one end. Cell wall firm but not
very robust. Filaments unbranched. Some
cells along the filament have ring-like trans-
verse lines at the swollen end (cap cells).
Cells 10-40 μm wide, 2-5 times as long as
wide....................... Oedogonium
41 (38) (a) Chloroplast a ring or is plate-shaped -
extending 1/3 to most way round the cell (at
right angles to the long axis). One or more
pyrenoids. Starch test positive . ......... 42
(b) Cells cylindrical or slightly barrel-
shaped, 2-6 times as long as wide. Chloro-
plasts one to many, curved discs or plate-
shaped with no pyrenoids. Cell walls may
fragment into H-pieces. Starch test negative
............................. Tribonema
Oedogonium cells form long, unbranched,
filaments. The chloroplast is parietal and net-
like. Cells are rectangular and longer than
 
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