Dasyphila preissii Sond.

Scientific Description

Habit and structure. Thallus mid to dark red-brown, 5–20 cm high, consistently distichously branched for 4–5 orders with alternate lateral branches throughout, axes and branches terete or very slightly compressed, densely corticated with rhizoids from close to apices with the whorl-branchlets largely outside the cortication. Holdfast discoid, rhizoidal, 1–3 mm across; epilithic or epiphytic on larger algae. Structure. Apical cells dividing transversely or slightly obliquely, subapical cells cutting off 6 whorl-branchlets in a largely alternating sequence, with lateral branches arising from the first or fourth formed whorl-branchlet (2–)4(–6) axial cells apart. Axial cells enlarging from 6–10 µm in diameter and L/D 1–1.2 just below the apices to 300–400 µm in diameter and L/D 1.5–4 in lower parts, becoming corticated by descending rhizoidal filaments from the basal cell of whorl-branchlets, rhizoids 5–8 µm in diameter with cells L/D 4–8, forming a dense layer 200–500(–800) µm thick. Whorl-branchlets 300–400 µm long, basal cells (becoming buried in cortex) 10–18 µm in diameter and L/D 1–1.5, branching above with usually 3 filaments then laterally branched with ultimate branches several cells long, 8–11(–15) µm in diameter and L/D 1–1.3; gland cells absent. Cells uninucleate; rhodoplasts discoid.

Reproduction. Gametophytes dioecious. Procarps borne on the basal cell (which acts as the supporting cell) of young whorl-branchlets, in succession as the apex elongates but only one maturing at each tip. Carpogonial branches 4-celled, with an auxiliary cell cut off from the supporting cell and dividing transversely to form a lower cell which pit-connects with the axial cell and an upper gonimoblast cell which develops elongate stalk cells each bearing a rounded group 90–200 µm across of carposporangia 10–15 µm in diameter, situated at branch apices and covered by adjacent elongate whorl-branchlets but not a special involucre. Spermatangia are borne on short branches on outer cells of whorl-branchlets, ovoid, 3–5 µm in diameter. Tetrasporangia occur terminally on end cells of whorl-branchlets, subspherical, 25–35 µm in diameter, tetrahedrally divided.

Distribution. Geraldton and Houtman Abrolhos, W. Aust., to Wilsons Promontory, Vic., and N Tas.

[After Wollaston & Womersley in Womersley, Mar. Benthic Fl. Southern Australia IIIC: 68–70 (1998)]