Glossary - Freshwater Algae: Identification, Enumeration and Use as Bioindicators - page 253

Glossary

Acicular Needle-shaped Benthos Living on the bottom, on the sediment

surface or rocks

Acuminate Tapering gradually towards the apex

BF Bright field light microscopy

Akinete A resting spore with thickened walls
formed from a vegetative cell in blue-green algae,
usually much larger than other vegetative cells

Bifurcate Forked into two branches

Biseriate A double row of cells or pores on a cell
wall

Alternating series A group of cells arranged side
by side but with every other cell displaced either up
or down relative to the mid-line (contrast with linear
series)

Bloom A dense growth of algae that visibly
discolours the water
Branching (true) Along the length of a filament
one cell gives rise to two or more cells one of which
continues the main axis whilst the others grow at an
angle to produce an additional filament (the branch)

Annular Shaped like a ring

Anterior Front end, i.e. the end at the front of
motile forms, or top end

(false) Side growths occur along a filament but they
are formed by a second filament growing sideways
and not by a single cell giving rise to two or more
others which themselves form lateral branches

Apical axis The axis linking the two poles (ends)
of the cell

Araphid Without a raphe system on either valve

Bulbous Bulb-like, swollen at one end

Arcuate Bow-shape, strongly curved

Calyptra A hood or cap-like covering usually
appearing on the apical cells of some filaments

Areolae Regular perforated markings on the wall
of a diatom forming a distinct pattern

Capitate With one or both ends of a cell swollen
into a head Attenuate Narrowing to a point

Carinal dots Dots or short bar-like markings
spaced evenly along the keel (at one margin) edge
of some diatoms (particularly Nitzschia )

Auxospore A resting spore formed by sexual activ-
ity or vegetative activity in some diatoms that allows
size restitution of the cell to occur

Central nodule A thickening on the wall of a
diatom at the centre between the raphe endings

Axial area A clear or hyaline area running along
the apical axis usually containing the raphe