Haplodasya urceolata (J.Agardh) Parsons

Scientific Description

Habit and structure. Thallus light to dark red-brown, (1–)5–15 cm high, with one to several erect axes laterally and radially branched for 3–4 orders, pyramidal in form, axes and branches terete, with 5 (rarely 4) pericentral cells, corticated from close to apices, clothed with branched rhodoplastic trichoblasts, denuded below. Attachment by a mass of tissue with the host receptacles; epiphytic on several species of Cystophora (C. intermedia, C. subfarcinata, C. moniliformis, C. congesta, C. retorta) and on Carpoglossum confluens, but not on Cystophora siliquosa. Structure monopodial, apical cells dome shaped, trichoblasts arising on a one quarter or one fifth spiral close to apices, with (usually) 5 pericentral cells cut off from 8–10 segments below apices in alternating sequence. Young branches 100–200 µm in diameter with segments L/D 0.8–1.2, mature corticated axes 200–600 µm in diameter. Trichoblasts formed spirally, on each segment, 0.5–2 mm long, with spirally arranged branches, basally branched 2 or 3 times, 1–2 cells apart, with long unbranched ends, basal and mid cells 30–60 µm in diameter and L/D 2–7; tapering gradually to upper cells 15–30 µm in diameter and L/D 2–8; adventitious monosiphonous filaments absent apart from on basal cells of trichoblasts. Cortication commencing 15–20 segments from apices, becoming heavy on lower axes with inner cortical cells of similar size to pericentral cells, then decreasing to small outer cortical cells. Lateral branches arising from trichoblasts. Cells uninucleate; rhodoplasts discoid.

Reproduction. Gametophytes dioecious. Procarps arising on the second or third segment of a trichoblast, which develops 5 pericentral cells, the last formed bearing a sterile cell group and a 4-celled carpogonial branch. Carposporophyte with a basal fusion cell and branched gonimoblast bearing clavate terminal carposporangia 25–35 µm in diameter. Cystocarps sessile or short-stalked, urceolate, 350–650 µm in diameter, with a short, slightly flared neck; pericarp ostiolate, with about 12 erect filaments, each cell with 2 isodiametric outer cells and 1–2 layers of smaller cortical cells. Spermatangial organs borne as branches of trichoblasts, elongate-lanceolate, 100–250 µm long and 35–55 µm in diameter, with 1–2 basal and apical sterile cells, without trichoblasts themselves, with the axial cells bearing 3 pericentral cells forming inner initials and an outer layer of spermatangia. Tetrasporangial stichidia borne as ultimate branches of trichoblasts or adventitious filaments, 180–550(–700) µm long and 80–110 µm in diameter, with 1–4 sterile basal and 1–2 sterile apical cells, without trichoblasts themselves, with 4 pericentral cells and 8–12 fertile segments, sporangia in a straight longitudinal row, 45–90 µm in diameter, with 2 pre-sporangial and 1 post-sporangial cover cells.

Distribution.Cape Leeuwin, W. Aust., to Port Fairy, Vic.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 243–245 (2003)]