Delisea hypneoides Harv.

Scientific Description

Habit and structure. Thallus medium to dark red-brown, 10–40 cm high, much branched irregularly and alternately, with distichous branching only close to apices, branches slender, slightly to moderately compressed, 200–600 µm broad above, 0.5–1 mm broad and only slightly compressed below where often denuded of ramuli. Lesser branches with alternate ramuli, at first distichous near the apices but soon flexed so that the distichous arrangement is lost, ramuli terete, simple or with 1–3 branches, (0.5–)1–2(–3) mm long and 100–200 µm in diameter near their bases. Attachment to the host by curled branchlets with small discoid pads; epiphytic (on Amphibolis and various algae) or possibly epilithic. Structure uniaxial, with a small apical cell, the subapical cells each cutting off two pairs of lateral and transverse periaxial cells, the lateral of the first pair producing the more strongly developed filament forming the originally distichous and alternate ramuli, with the lateral cell of the second pair usually remaining ovoid and not forming a distinct filament, or occasionally developing to form an opposite ramulus; the transverse periaxial cells contribute to the cortex. Main branches 12–20 cells thick, the axial filament 30–60 µm in diameter, developing a thin sheath of small cells; inner cortical cells ovoid, 40–100 µm in diameter, becoming thick walled and with few intermixed small cells; outer cortical cells angular, 4–8 µm across, usually with few, scattered, gland cells; hairs often profuse; older axes with a secondary cortex of anticlinal filaments. Rhodoplasts discoid, becoming ribbon like in inner cells.

Reproduction. Gametangial thalli dioecious. Carpogonial branches 3-celled, borne on the first cell of shorter lateral periaxial filaments. Carposporophyte associated with the less well developed lateral periaxial filament, with a basal fusion cell, an adjacent group of darker staining (nutritive) filaments, and a short tuft of branched gonimoblast filaments with terminal elongate-ovoid carposporangia 20–35 µm in diameter. Cystocarps lying between ramuli, sessile and immersed, 500–800 µm across, with a thick pericarp (with internal branched cell filaments) and a protruding beak with a prominent ostiole. Spermatangial sori covering lower parts of ramuli and on lesser branches, with the outer cortical cells cutting off 2–3 elongate, tapering initials producing 2–3 elongate spermatangia 2–3 µm in diameter. Tetrasporangia unknown.

Distribution.Point Peron, W. Aust., to Walkerville, Vic., and northern Tas.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIB: 340–342 (1996)]