Champia parvula (C.Agardh) Harv.

Scientific Description

Habit and structure. Thallus red to red-brown, erect and spreading, 2–11 cm high, much branched with one to several axes irregularly radially branched for 3 or 4 orders. Axes and branches terete, 1–1.5 mm in diameter below, tapering gradually to branchlets 0.3–0.5 mm in diameter, young branches slightly constricted at diaphragms, segments L/D 1–1.5, ends straight, apices rounded; diaphragms distinct throughout most of thallus, obscured near older bases. Holdfast small, discoid, with occasional haustorial pads; epilithic or epiphytic on Amphibolis. Structure multiaxial, with 10–15 apical cells, developing a cortex of angular cells mostly 20–50(–60) µm across and mostly L/B (1–)2–3, with small cells cut off from their corners and forming a more prominent outer cortex (up to 2–3 cells thick) on older axes; longitudinal filaments peripheral only, usually with 2(–3) complete cells (with secretory cells) and two part cells between the diaphragms. Rhodoplasts discoid, usually in chains.

Reproduction. Gametangial thalli dioecious. Carpogonial branches 4-celled, borne on a cortical (supporting) cell together with a 2-celled auxiliary cell branch. Carposporophyte with a basal fusion cell, branched gonimoblast filaments of ovoid cells and terminal, ovoid to obconical, carposporangia (40–)50–90 µm in diameter. Basal nutritive tissue slight, inner cells of pericarp stellate and separating. Cystocarps scattered, subspherical to urceolate, 0.7–1.3 mm in diameter, pericarp 60–130 µm and 3–5 cells thick, ostiolate. Spermatangia covering segments near apices of young branches, cut off from branched filaments of initials, ovoid, 3–5 µm in diameter. Tetrasporangia scattered, transformed from cortical cells, (50–)60–120 µm in diameter, tetrahedrally divided.

Distribution.Widely reported from most temperate waters, but many records need verification.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIB: 129 (1996)]