Stilopsis harveyana Kylin

Scientific Description

Habit and structure. Thallus medium brown, moderately mucoid, slender, much branched subdichotomously and laterally, usually 10–35 cm long with cylindrical, slightly tapering branches 0.5–1 mm in diameter below and 100–200 µm in diameter near the apices, probably attached by a small holdfast or entangled with the host, epiphytic. Medulla of a single axial filament each cell of which cuts off 4–5 cortical laterals which divide further. Cortex 100–400 µm and 4–5 cells thick, pseudoparenchymatous, with large, elongate inner cells 20–30 µm in diameter grading to smaller outer cells, usually not becoming hollow. Primary assimilatory filaments rudimentary, covering the thallus surface, papillose, with filaments 15–25 µm and 1–2(–3) cells long, the terminal cell subspherical to ovoid, 8–12 µm in diameter; older parts of branches often denuded. Secondary assimilatory filaments developed in older branches as scattered and somewhat spreading tufts, with filaments 60–90 µm and 4–6 cells long, slightly clavate with the terminal cell subspherical to ovoid, 9–12 µm in diameter. Phaeoplasts in assimilatory filaments and outer cortical cells in denuded parts, several per cell, discoid, each with a pyrenoid; physodes not seen. Phaeophycean hairs among primary assimilatory filaments and in secondary tufts, 8–12 µm in diameter. Growth apical, by the single axial filament and lateral development of the cortex.

Reproduction. Unilocular sporangia ovoid to broadly clavate, 30–45 µm long and 20–30 µm in diameter, borne at base of secondary assimilatory filaments. Plurilocular sporangia unknown.

Distribution. King George Sound, W. Aust., and from Redbanks, Kangaroo I., S. Aust., Burraneer, N.S.W., Port Arthur, Tas.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 135 (1987)]