Webervanbossea kaliformis (J.Agardh) G.De Toni

Scientific Description

Habit and structure. Thallus medium to dark red-brown, mucilaginous, 10–25 cm high, with percurrent axes bearing hollow, segmented laterals irregularly radially for 2–4 orders, arising from any position on parent segments but mainly apically on lesser branches with some segments without laterals; segments with a slender constriction; lower segments elongate-ovoid, 2–4 cm long and 5–10 mm in diameter, decreasing in size to upper segments mostly 0.5–2 cm long and 2–4 mm in diameter. Holdfast discoid, 1–3 mm across; epilithic. Structure multiaxial, with a cortex 20–45 µm and 3–4 cells thick, outer cells in short anticlinal chains of 2–3 cells, arising from a layer of ovoid cells 6–10 µm in diameter over the medullary cells, surface rosettes not apparent, outer cortical cells ovoid and 3–4 µm in diameter; medulla as a distinct layer one cell thick, cells ovoid and 40–100 µm in diameter with walls (6–)10–25 µm thick, with smaller cells lying between the larger cells over their joins and under the cortex. Long, branched, slender filaments extend from stellate cells on some inner medullary cells and bear lateral, ovoid, secretory cells 6–10 µm in diameter, and in older segments lax, branched, slender filaments are common within the mucilage-filled cavity. Constrictions are partitioned by essentially monostromatic layers of large cells, with small irregular cells and filaments forming a thin layer on each side. Rhodoplasts discoid, in chains in inner cells.

Reproduction. Gametangial thalli probably dioecious. Carpogonial and auxiliary branches not observed. Carposporophytes 350–450 µm across, with a basal, erect, fusion cell and a dense mass of ovoid carposporangia each 15–30 µm in diameter, with younger lobes developing. Basal nutritive tissue relatively slight, erect filaments persistent, of stellate filaments with long arms. Cystocarps slightly protruding but largely immersed, 500–900 µm across, with a distinct layer of large medullary cells at their base; pericarp 100–200 µm and 10–15 cells thick, ostiolate. Spermatangia unknown. Tetrasporangia in scattered nemathecia 0.5–1 mm across and 120–180 µm thick. Paraphyses 6–8 cells long, lower cells elongate, upper ovoid and often branched, tetrasporangia lateral, pit-connected to a lower cell of the paraphyses, ovoid, (16–)20–40 µm in diameter, decussately divided.

Distribution.Isles of St Francis, S. Aust., to Walkerville Vic.

Habitat. W. kaliformis is essentially a deep-water species.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIB: 63 (1996)]