s A Field Guide to the British Seaweeds - NMBAQC

Phaeophyta Species
Group A Plants are generally large and cartilaginous in form, consisting of a
thick, tough and leathery frond. This group may take on a variety of
morphological forms composed of wide flat fronds, channelled fronds,
simple single blades and highly branched forms. These plants are not
hollow except for the presence of air bladders which may be found in
some species.
Group B Plants consist of a thick thread like form ranging from 1mm to 5mm
wide. These are often cylindrical but may also be slightly flattened but
are not hollow and do not contain air bladders. Some species may
appear as a single rope like plant, other species may be highly
branched and more delicate in form.
Group C Plants filamentous in form, tending to be very fine, delicate and hair
like. Generally consist of a main axis up to 1mm thick and numerous
filamentous branches usually less than 0.25mm. Branches may either
be uniformly arranged or irregular. Filaments may be long, short, stiff
or floppy, separated or tangled together into woolly cords. Usually less
than 15cm long, but may extend up to 30cm. Found growing
epiphytically on a host species or independently. Many species require
microscopic assistance for identification.
Group D Plant flattened and quite thin may be easily torn but generally quite
elastic. Consist of both branched and unbranched forms although not
numerously branched.
Group E Plants tubular and hollow from 2mm to 12mm wide. May be easily
torn as they can be quite thin and membranous.
Group F Plants forming distinct crusts or cushions on the rock and other hard
surfaces.
Reduced species list identification guide as required by the Water Framework Directive 26