Gattya pinnella Harv.

Scientific Description

Habit and structure. Thallus medium red-brown, 2–10 cm high, firm, with alternately pinnate erect axes arising from prostrate lower parts, branches sympodially branched, compressed in the plane of branching with constrictions depending on new growth phases, branches with a gelatinous sheath. Attachment by rhizoids; epiphytic on Amphibolis or larger algae. Structure. Apices with a row of 3–9 short cells 6–9 µm in diameter, axial cells enlarging below to 60–90 µm in diameter and L/D 2–4, basal axial cells lightly corticated with rhizoids; lateral branches arising from axial cells. Each axial cell with 3 (rarely 4) whorl-branches 250–450 µm long, closely adjacent, branched di- or trichotomously several times, basal cells 12–25 µm in diameter and L/D 1–2, adjacent cells L/D 5–6, tapering to subspherical terminal cells 5–8 µm in diameter. Cells uninucleate; rhodoplasts ovoid in smaller cells, elongate in larger cells.

Reproduction. Gametophytes dioecious. Procarps produced in place of a whorl-branchlet near apices, with a large supporting cell bearing a 4-celled carpogonial branch. Post-fertilization the carpogonium connects with the auxiliary cell via a connecting cell and produces an erect rounded gonimolobe and later lateral gonimolobes, each 150–220 µm across with ovoid carposporangia 25–35 µm in diameter. Carposporophytes occur in swollen branch ends. Spermatangia are cut off from terminal cells of whorl-branchlets, ovoid, 2–3 µm in diameter. Tetrasporangia occur on basal cells of whorl-branchlets, produced successively, sessile, subspherical, 45–60 µm in diameter, tetrahedrally divided.

Distribution.Houtman Abrolhos, W. Aust., to Westernport Bay, Vic., and N Tas.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 51 (1998)]