s A Field Guide to the British Seaweeds - NMBAQC

Group A
1. Plants completely flattened……………………………………………………2
1. Plants tubular or appearing slightly filiform…………………………………..3
2. Plants one cell thick only, forming a very delicate and thin membrane, may
tear very easily and with a sheet-like appearance almost translucent
2.
Monostroma sp.
Plants two cells thick, forming a tougher thicker sheet, often bright green in
colour Ulva lactuca
3. Cells usually 4-12um wide with a basal disc and no rhizoidal cells, small
filiform plants often found as a thin spongy mat or layer on Fucus or upper
shore rock surface Blidingia sp.
3. Cells greater than 12um, tubular plants, may be branched or unbranched often
found in dense patches covering vast areas of the upper and mid shore
attached by rhizoidal cells Enteromorpha sp.
Group B
1. Plants unbranched or few branches……………………………………………2
1. Plants highly branched………………………………………………………...6
2. Rhizoidal growths or false branching of 1-3 cells long, cells generally longer
than wide forming long filaments, forming a felty green mat at the top of the
shore Rhizoclonium tortuosum
2. Rhizoidal growths absent……………………………………………………...3
3. Plants with a reticulate (net-like) chloroplast…………………………............4
3. Plants with a single band/cup shaped or parietal chloroplast where the
chloroplast lines the inner cell wall Ulothrix sp.
Reduced species list identification guide as required by the Water Framework Directive 24