Phycodrys australasica A.Millar

Scientific Description

Habit and structure. Thallus medium red-brown, decumbent to more-or-less erect, 3–8 cm high, densely tufted with complanately branched primary and main blades 3–5 mm broad, bearing marginally lateral blades (1–)2–4 mm broad with slender, compressed to terete, basal constrictions 200–500 µm broad; blades linear to gently tapering, flat, apices acute to rounded, margins with short, blunt, dentations; all blades with a central midrib and relatively faint, paired, lateral veins. Attachment by small discoid holdfasts bearing 1–3 fronds, often with a stoloniferous base giving rise to further erect fronds; epiphytic, epizoic (e.g. on bryozoans) or epilithic. Structure. Apical cell conical, segmenting rapidly to an axial row (which soon becomes corticated) and lateral and transverse pericentral cells, the lateral cells producing second-order rows reaching the blade margin and from which third-order cells or short rows are cut off abaxially and adaxially in an irregular manner, giving a monostromatic blade (apart from the veins) of compact, isodiametric, irregular cells 20–30 µm across in surface view; lateral veins with central primary cells and a cortex 1(–2) cells thick; transverse intercalary divisions occur in the axial cells so that the second-order rows become separated by 2–5 axial cells as they develop into the lateral paired veins, with further lateral divisions of the daughter axial cells and the second- and third-order cells forming the expanded blade. The margins of the blade bear short dentations 30–50(–200) µm long, the larger ones corresponding to the vein endings and occasionally developing as lateral blades. Mature cells multinucleate; rhodoplasts discoid.

Reproduction. Gametophytes dioecious. Procarps scattered on both sides of blades, probably with a 4-celled carpogonial branch and 2 sterile groups. Carposporophytes with a small basal fusion cell and chains of ovoid carposporangia 15–30 µm in diameter. Cystocarps 300–700 µm across, few per blade, protruding mainly on one side of the blade, ostiolate; pericarp 90–140 µm and 5–8 cells thick, thicker around the ostiole. Spermatangial sori on both sides of blades between midrib and margins, covering the lateral veins, with each primary cell covered by 8–10 cortical cells each of which produces 2–4 spermatangia. Tetrasporangial sori scattered, often close to margins, with tetrasporangia in 2 layers, cut off from inner cortical cells and covered with a layer of small outer cortical cells, subspherical and 30–50 µm in diameter.

Distribution.Hamelin Bay, W. Aust., Port Noarlunga, S. Aust., Port Phillip Bay and Westernport Bay, Vic., and N.S.W. and Norfolk and Lord Howe I.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 73 (2003)]