Heterosiphonia crispella (C.Agardh) M.J.Wynne

Scientific Description

Habit and structure. Thallus small, to 10 mm in height, upright, attached by rhizoidal filaments arising from lower cells, with 1–3 percurrent primary axes arising from near the base. Primary axes polysiphonous, ecorticate, with 6 pericentral cells, these slightly offset in successive segments; branching distichous with pseudolaterals arising every 2 segments. Polysiphonous segments to 80 µm in diameter near apex of plant, L/B ± 1, broadening to 220 µm near base, L/B ± 0.6. Pseudolateral branches to 1.2 mm long, curved towards apex, monosiphonous except for basal and often suprabasal polysiphonous segment (these with four pericentral cells), dichotomously divided every two cells; lower cells 50–65 µm in diameter, tapering slowly to outer cells 35–40 µm; apical cells pointed but without a spine, with cells 18–25 µm in diameter.

Reproduction. Reproductive structures not seen.