Doxodasya bolbochaete (Harv.) Falkenb.

Scientific Description

Habit and structure. Thallus light to dark red-brown, 10–70 cm high, with denuded, branched, cartilaginous main axes 1–2(–3) mm in diameter, bearing irregularly (often clustered) laterals 10–20 cm long, branched for 1–3 orders, upper and mid branches clothed with small discrete branch systems of short, quadrifarous, shoots bearing rhodoplastic trichoblasts spirally. Cortication commences about 50 segments from apices, first with rhizoidal filaments lying outside and between the pericentral cells and later covering the branch and becoming heavy on lower axes; the 4 pericentral cells (sometimes with 1–2 more interposed cells) remain clear in transverse section, and the outer cortex is of elongate cells. Holdfast discoid, 1–3 mm across; epilithic. Structure monopodial, with 4 pericentral cells formed in alternating sequence 20–27 segments below apices, each axial segment bearing a simple (or basally branched) trichoblast, spirally arranged with the sub-basal cell forming a short shoot; adventitious filaments absent. Short shoots 1–4 mm long, with an axis of 15–30 small isodiametric cells bearing spirally arranged trichoblasts; these short shoots give a characteristic appearance to the branches. Trichoblasts slender, 2–4 mm long, 12–25 µm in diameter and scarcely tapering, basal cell short (L/D about 1), mid and upper cells L/D (3–)4–8, terminal cell tapering with a rounded tip. Cells uninucleate; rhodoplasts discoid.

Reproduction. Gametophytes dioecious. Procarps occur 2–3 cells from base of a trichoblast on a short shoot, developing 5 pericentral cells with the fifth bearing a sterile group of 4 cells and a 4-celled carpogonial branch. Carposporophytes with a basal fusion cell bearing erect gonimoblast filaments with clavate terminal carposporangia 25–40 µm in diameter, replaced from below. Cystocarps ovoid to globose, 0.8–1.5 mm in diameter, with a stalk 0.5–2 mm long but no neck; pericarp ostiolate, several cells thick with small cortical cells. Spermatangial organs on trichoblasts of short shoots, with several sterile basal and apical cells, 100–400 µm long and 40–65 µm in diameter, with 10–15 fertile segments of 3 pericentral cells (subdividing to 5–6) cutting off an outer layer of spermatangia. Tetrasporangial stichidia formed from axes of the short shoots, 0.3–1(–1.6) mm long and 200–250 µm in diameter, the tetrasporangia formed in decussate pairs with 2 pre-sporangial and 1 post-sporangial cover cells; tetrasporangia 70–110 µm in diameter.

Distribution.Houtman Abrolhos, W. Aust., around southern Australia to Walkerville, Vic., and the N coast of Tas.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 264–267 (2003)]