Dasyclonium flaccidum (Harv.) Kylin

Scientific Description

Habit and structure. Thallus medium to dark red-brown, basally attached to host (or rock?), above free and 1–15 cm long; indeterminate axes irregularly branched and bearing distichous, alternate, determinate laterals (0.6–)1–2 mm long from each second segment; determinate laterals pectinate, main branch usually curved downwards, complanately branched with simple, exogenous branches from each second cell, these branches with monosiphonous ends 5–12 cells long or sometimes entirely monosiphonous. Lateral indeterminate axes arising endogenously from a segment above a determinate lateral, separated usually by 3 determinate laterals, occasionally developing into longer axes. Attachment by rhizoids; epiphytic on various algae, occasionally epilithic. Structure. Apex slightly curved, apical cells dome-shaped, 15–30 µm in diameter. Indeterminate axes with 6 pericentral cells, 130–350 µm in diameter, segments L/D 0.4–1. Determinate laterals below with 3 pericentral cells, 60–150 µm in diameter below with segments L/D 0.4–1.2; pericentral cells L/D (1.5–)2–3, monosiphonous parts 35–100 µm in diameter with cells L/D 1–5, end cell mucronate. Trichoblasts apparently absent. Rhizoids usually in pairs from adjacent axial pericentral cells, not cut off, with digitate haptera. Cells uninucleate, larger cells multinucleate; rhodoplasts discoid to slightly elongate.

Reproduction. Female plants unknown. Spermatangial organs tri-radiate, developed from the lower parts of determinate lateral branches, with a single basal and 3–5 apical sterile segments 150–600 µm long and 130–230 µm across, each flange with a marginal row of isodiametric sterile cells. Tetrasporangial branches arising endogenously from the segment above each determinate lateral, curved upwards towards the axis and developing short cellular outgrowths; tetrasporangia in series of 4–6, 80–140 µm in diameter, with 3 (divided) cover cells.

Distribution.Houtman Abrolhos, W. Aust., to Robe, S. Aust., and N Tas. Japan.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 321–323 (2003)]