Polycerea zostericola (Kütz.) Kylin

Scientific Description

Habit and structure. Thallus medium brown, mucoid, relatively soft, much branched with frequent short laterals, cylindrical, 2–20 cm long and 1–2 mm in diameter, epiphytic on Posidonia australis, P. sinuosa and Amphibolis antarctica. Medulla multiaxial, becoming hollow, of parallel, cylindrical, longitudinal filaments 20–40 µm in diameter with cells L/B 3–8, slenderer at the periphery, with only slight development of hyphae. Subcortex slight, usually of 1(–2) cells each 10–16 µm in diameter and L/B (1–)1.5–3. Cortical filaments arising in small groups from subcortical cells, forming a moderately dense layer with slightly curved filaments 100–160 µmand 8–13 cells long, lower cells 6–10 µmin diameter and L/B 1.5–3, with the upper 3–4 cells larger, subspherical, increasing in diameter upwards, with subterminal cells l2–20 µm in diameter and the terminal cell subglobose to slightly ovoid, 22–32 µmin diameter, and 1.5–2 times the diameter of the subterminal cell. Phaeoplasts several per cell, discoid, probably each with a pyrenoid; physodes sparse. Phaeophycean hairs frequent, arising from outer subcortical cells, 8–16(–18) µmin diameter.

Reproduction. Plurilocular sporangia borne on pedicels of 4–6 cells from the subcortical cells, usually once or twice furcate or branched, with the arms tapering or lanceolate, multiseriate, 30–60 µmlong and 12–16 µmin diameter. Unilocular sporangia borne on basal cells of cortical filaments or on upper subcortical cells, sessile, ovoid, 35–60 µmlong and 25–40 µm in diameter.

Distribution. From Jurien Bay to Esperance, W. Aust., as a summer annual.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 126–127 (1987)]