Cladophora laetevirens (Dillwyn) Kütz.

Scientific Description

Habit and structure. Thallus light to medium green, forming dense tufts 2–10 cm high with pseudo-dichotomous axes from a small group of rhizoids from cells in the basal region; epilithic; filaments tapering only slightly, branched from almost every cell above with often somewhat falcate and unilateral branchlets. Growth acropetal and mainly apical above, with intercalary divisions in the mid and lower thallus cells thus separating the laterals by 2–6 cells but with new laterals often arising below intercalated cross walls; each parent cell bearing 1–2(–3) laterals mostly at about 45°; basal cross wall of young laterals usually oblique to parent cell, later becoming almost horizontal. Apical cells 40–70(–80) µm in diameter, L/B 4–11, cylindrical to slightly broader in upper half, apically rounded; ultimate branch cells 40–75 µm in diameter, L/B 4–7; lower thallus cells (100–)120–160(–180) µm in maximum diameter, L/B 2–8(–10); ratio of lower cell to apical cell diameters 2–3; cell walls moderately thin (2–4 µm) in apical cells, thicker below (6–10 µm).

Reproduction. By apical and subapical cells forming zooidangia; elsewhere by biflagellate gametes and quadriflagellate zoospores.

Distribution. Widely distributed along tropical to warm-temperate Atlantic coasts of Europe, W. Africa and America (incl. Mediterranean). In southern Australia, from South Perth, W. Aust., to Manly, N.S.W.

[After van den Hoek & Womersley in Womersley, Mar. Benthic Fl. Southern Australia I: 200 (1984)]