Phylum: Rhodophyta   Family: Delesseriaceae

Membranoptera alata  (Hudson) Stackhouse, 1809

Winged Weed

Common on the lower shore and below, growing on rocks and on Laminaria stipes. The thallus has wing-like side growths and young growths are blade-like. Can look quite battered in winter

References: 
Maggs, C.A. & Hommersand, M.H. (2013 reprint) Seaweeds of the British Isles, Volume 1 Rhodophyta, Part 3A Ceramiales.
Bunker, F. StP. D., Brodie, J., Maggs, C.A. & Bunker, A.R. (2017 second edition) Seaweeds of Britain and Ireland.