A Key to the More Frequently Occurring Freshwater Algae - Freshwater Algae: Identification, Enumeration and Use as Bioindicators - page 147

(but see also Coleochaete which, when older,
forms a mass or disc of cells that appear multi-
seriate).

10 (9) (a) Filaments branched (although the
branching can be scarce and difficult to find -
hence the need to look along several fila-
ments to confirm the situation) with branches
arising in tufts (embedded in mucilage)
or as less frequent and more tapered
bristles............................... 11

20 μm

(b) Filaments encrusting on stones or
macrophytes forming single or packed lay-
ers of cells, green, red or brown in colour
..................................... 12

11 (10) (a) Filaments loosely embedded in copi-
ous mucilage. Main filament axis with tufts
of branches arranged at regular intervals
...................... Batrachospermum

200 μm

Batrachospermum produces large multi-
branched filaments in a mucilaginous or
gelatinous mass, similar to frog spawn. The
overall appearance of the filaments is that
they are beaded. There is a main large axis
with regular whorls of smaller branches.
Chloroplasts lack pyrenoids and are ribbon-
like (several per cell), olive brown to reddish
or grey-blue in colour. The whorls may be
>

Figure 4.3 Vaucheria . Top: Detail from surface of fil-
ament (DIC image) showing numerous discoid chloro-
plasts. Bottom: Low power view of filaments showing
absence of cell walls.

with or without pyrenoids. The usual storage
products are oil and fat, very rarely starch.
Branching does occur but is irregular. Fila-
ment 20-140 μm wide. The various species are
identified mainly by their reproductive struc-
tures. Widespread and may form green mats
of tangled filaments in shallow freshwaters,
on stones and damp soil. May also occur in
salt marshes and brackish water muds. Xantho-
phyta. Plate II. Fig. 4.3.

1 mm in diameter. Widespread and with a
characteristic appearance. Found in streams
and pools/bogs, often in warmer waters.
Rhodophyta. Plate II. Fig. 4.4a.

Audouinella has simple branched filaments
with both prostrate and erect branches. Cells
cylindrical with parietal chloroplasts. Repro-
duction by monospores. Common epiphyte.
Rhodophyta. Fig. 4.4b.

(b) Filaments with normal cross walls, not
siphonaceous . ........................... 9

(b) Plants without regular tufts of branches.
Thickened areas along stem. ..... Lemanea

9 (8) (a) Filaments multiseriate, that is, columns
of cells in many parallel or radiating rows.
Branches may or may not be present . . .... 10 The thallus of Lemanea is cartilaginous and

thus has an erect posture being attached at
the base. The bristle-like 'stems' can grow

(b) Filaments not multiseriate ............ 13