Glossary - Freshwater Algae: Identification, Enumeration and Use as Bioindicators - page 258

Spathulate A wide upper part tapering gradually
to form a stalk

Triradiate With three arms radiating out from a
central position

Truncate A cell with a flat top or end

Starch test When a solution of iodine is applied to
the specimen, if starch is present a blue or blue-black
colour is produced. See iodine test above.

Tychoplankton Plankton in shallow inshore
waters, often in amongst plants and weeds, and
detached from a surface and are therefore chance
members of the plankton

Stauros A thicker hyaline region on a diatom valve
extending from the central nodule to the margins of
the valve

Undulate With a wavy surface or edge

Stellate Star-shaped

Unilateral Pertaining to one side only

Sternum A hyaline region running along the long
axis of a diatom valve in diatoms that have no raphe
(araphid) with striae either side

Uniseriate Formed as a single row (of pores in
diatoms or cells in other algae)

Vacuole A space in the cytoplasm lined by a mem-
brane filled with fluid or occasionally granules

Stigma see eyespot

Strand A group of cells joined side by side to form
a filament-like structure (see also ribbon)

Valve One of the two halves of a diatom frustule
Valve mantle The margin of a diatom valve some-
times with a definite slope or structure

Striae Delicate, sometimes long narrow markings
or lines on the valve of a diatom

Valve view The view of a diatom cell looking at the
valvefaceandnotseeinganyoverlappingportions(as
opposed to the girdle view)

Sub-pyramidal Shaped like a pyramid but with the
top cut off

Sulcus A narrow pair of furrows that may be found
in the girdle area of some filamentous diatoms

Ventral The less convex margin of a dorsiventral
cell, e.g. in the diatom Cymbella

Test A rigid urn or pot-shaped surround to a cell
with a space between it and the cell inside

Water bloom A dense growth of planktonic algae
that distinctly colours the water and may form a scum
on the surface

Thallus A plant body with little differentiation into
tissues

Whorls Several branches arising at the same point
around a main axis, e.g. in Chara

Theca seeatest

Xanthophylls A yellow, carotene derived, photo-
synthetic pigment

Transapical At right angles to the apical or long
axis in diatoms

XRMA X-ray microanalysis

Trichome A thread-like series of cells, exclusive of
the sheath, found in blue-green algae

Zoospore A motile sexual spore

Trichotomous Branching or dividing to form three
equal-sized branches

Zygospore A thick-walled resting spore formed
from the fusion of two gametes