Corallina officinalis L.

Scientific Description

Habit and structure. Thallus pink-grey to medium red-purple, fading to light grey, (1–)2–6 cm high, usually in tufts of several to numerous erect fronds from a crustose base. Fronds pinnately and complanately branched for 2–3 orders, usually from each intergeniculum with one or two lateral branches from each shoulder, commonly denuded below. Intergenicula subterete to slightly compressed near the base of axes, compressed above and broader apically, usually 500–1000(–1500) µm long and 500–800(–1500) µm broad, edges rounded in section. Lateral branches distinctly slenderer, simple or branched, terete and tapering to slightly broader above, 200–300(–500) µm in diameter, intergenicula 700–1500 µm long; some terminal intergenicula flat and spathulate. Holdfast discoid, becoming crustose and (0.5–)1–2 cm across; epilithic or on mollusc shells. Structure multiaxial, intergenicula of (8–)10–20(–25) tiers of medullary cells 30–60 µm long and 6–10 µm in diameter, with frequent lateral cell-fusions; ends of tier cells usually not aligned. Cortex of splaying filaments from the outer medullary filaments, cells 4–10 µm in diameter and L/D (1–)2–4, with small epithallial cells. Rhodoplasts discoid to laminate. Genicula of single tiers of slender, cells 180–350 µm long and 4–7 µm in diameter, walls staining darkly.

Reproduction. Gametangial thalli dioecious. Conceptacles uniporate, axial, swollen, terminating lateral branchlets or occasionally (female and tetrasporangial) bearing short slender branchlets. Carposporangial conceptacle chambers 250–400 µm in diameter, 300–320 µm high, roofs 150–240 µm thick, fusion cells 90–200 µm in diameter and 6–11 µm thick; carposporangia 30–80 µm in diameter. Male conceptacle chambers 250–480 µm in diameter, 100–300 µm high, roofs 200–600 µm thick. Tetrasporangial conceptacle chambers 300–450 µm in diameter, 300–600 µm high, with neck canal 200–250 µm long through the thickened roof; tetrasporangia 180–240 µm long and 55–85 µm in diameter, zonately divided.

Distribution.Widespread in temperate seas.

Habitat. C. officinalis is the commonest geniculate coralline alga just above low tide level, often forming a distinct turf in the lower eulittoral zone.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIB: 291–293 (1996)]