Bonnemaisonia asparagoides (Woodward) C. Agardh
Description: Gametophyte (above) with feathery fronds, much branched, to 250 mm long, main axis cylindrical or slightly compressed, to 3 mm wide, from small discoid base. Branches alternate, distichous, covered with alternating, spinelike corticated ramuli about 2 mm long in one plane. Tetrasporophyte a minute prostrate disc 2-4 mm diam.
Habitat: The gametophytes are summer annuals (May-September) found on rock, very low intertidal or subtidal (to 30 m in Britain and Ireland), widely distributed, frequent in the subtidal. Sporophyte subtidal, on shells, stones, etc., very rarely found.
Similar species: Bonnemaisonia hamifera is less common and more seasonal (March to June, inclusive, and has distinctive and unique crozier-shaped modified branches that hook on to other algae; Naccaria wiggii even less common and has branchlets that grow radially on the axes.
Key characteristics: Short, almost spiny branchlets in two rows; specimens also degenerate very quickly unless kept in large amounts of seawater and in a cool place.
Photograph © Bernard Picton, Ulster Museum