s A Field Guide to the British Seaweeds - NMBAQC

8. Thallus consisting of a large wide flat frond…………………………….........9
8. Thallus rope-like extending from a button or mushroom shaped holdfast,
frond often very long, sometimes flat and divided Himanthalia elongata
9. Flat expanded part of thallus not divided, with wavy edge and crinkly centre
Laminaria saccharina
9. Main thallus smooth and generally divided, giving large finger like
appearance……………………………………………………………………10
10. Holdfast a large and warty bulb with ribbon-like, wavy stipe
Saccorhiza polyschides
10. Holdfast simple and claw shaped……………………….……………………11
11. Stipe smooth and flexible and slightly flattened at the top, can be almost
entirely undivided in sheltered areas Laminaria digitata
11. Stipe stiff, round and upright, generally rough and covered with red algal
epiphytes Laminaria hyperborea
Group B
1. Plant completely unbranched, cylindrical bootlace extending to 8m in length.
Chorda filum
1. Plant variously branched……………………………………………………....2
2. Branching mostly alternate, frond flattened with long main axis, older plants
exhibit short spine-like branchlets giving a serrated appearance.
Desmarestia aculeata
2. Branching mostly irregular……………………………………………………3
3. Branches numerous, often with a covering of fine hairs, slightly gelatinous
and slippery. Chordaria flagelliformis
3. Branches more coarse in texture. Dictyosiphon foeniculaceus
Reduced species list identification guide as required by the Water Framework Directive 28