2
Notes on the illustrations:-
A, Chlamydomonas. There are over 1000 species of this tiny swimming alga (or
flagellate), mostly under 20 mm long, many badly described, many seen once only!
B, Haematococcus, another small flagellate. The very common H. pluvialis stores
oil coloured red by carotenoid pigments, and this gives a red colour to bird baths
etc.
C, Gonium. A colonial flagellate in the form of a flat plate.
D,E.Two species of Scenedesmus, a colonial non-motile alga up to 30 mm wide.
F, Actinastrum, a radially arranged non-motile colony, with cells up to 25 urn long.
G, Pediastrum. A colony in the form of a flat plate uo to 1000 mm across.
H, Spirogyra, I, Oedogonium, J, Cladophora, K, Zygnema, and N, Vaucheria, five
genera of filamentous algae. These may form the fluffy masses often called
"blanket weed".
L, Closterium, and M, Cosmarium. These are desmids, related to Spirogyra. There
are many desmids, often very beautiful, varying from 10 to 1000 (mm long.
P, Euglena, Q, Phacus, and R, Trachelomonas, are flagellates related to each other,
and are often abundant in farm ponds and other highly nitrogenous waters.
S, Gomphonema, T, Navicula and U, Gyrosigma, are diatoms, with a silica wall or
"frustule", the frustule of each species having its characteristic pattern. These
frustules may endure for thousands or even millions of years, and are often useful
in dating sediments.
V, Batrachospermum, the frog-spawn alga, may be up to several centimetres long.
Although brown or green in colour, it is related to the red seweeds.
W, Oscillatoria, X, Anabaena, and Y, Microcystis are blue-green algae, related to the
bacteria. Some species may float to the surface in calm weather and can form the
paint-like often toxic water blooms.
Hilary Belcher, 23 Pepys Way, Girton, Cambridge CB3 0PA.
(Drawings by Erica Swale)