Griffithsia crassiuscula C.Agardh

Scientific Description

Habit and structure. Thallus light red, spreading, 9–26 cm high, subdichotomous many times, ecorticate, filaments constricted between cells and apically attenuate. Attached by rhizoids from basal cells; epilithic. Structure. Cells in upper thallus globose-ovoid, 1–1.5 mm in diameter and L/D 1.9–2.2; in mid thallus allantoid, or cylindrical with swollen ends (bone-shaped), 1.4–2.2 mm in diameter and L/D 1.7–3; basal cells cylindrical, 0.6–1.6 mm in diameter and L/D 2.8–4.

Reproduction. Gametophytes dioecious. Female axes 3-celled, associated with whorls of 12–17 polychotomous, hair-like, synchronic laterals, displaced laterally by continued growth of the vegetative apical cell. Procarp systems subapical, each with a sterile lateral cell and a supporting cell with an apical sterile cell and lateral 4-celled, recurved carpogonial branch; the inner of two post-fertilisation connecting cells fusing with the supporting cell which cuts off an auxiliary cell; post-fertilisation fusion cell columnar, bearing 1–3 gonimolobes terminally, most cells of which produce ovoid-clavate carposporangia, 35–55 µm in diameter. Carposporophytes lateral in the constrictions between cells. Two carposporophyte types exist, separated on their involucral branches. Type A produces 7–10 involucral branches in which the larger terminal cells are 320–450 µm long, regular and incurved. Type B produces 5–6 involucral branches with terminal cells 540–850 µm long, furcate or distinctly irregularly lobed. Hair-like synchronic laterals are successively produced and shed so that carposporophytes may be surrounded by several whorls in various stages of development. Spermatangia borne on numerous minute fascicles from the upper shoulders of usually only subapical vegetative cells, clustered in the constriction between cells. Initially a synchronic whorl of 6–8 fascicles resembling the initials of hair-like synchronic laterals develop, but this is soon followed by the production of numerous other fascicles, each consisting of an ovoid basal cell 10–20 µm in diameter bearing 5 branches dividing polychotomously 4–6 times, in which the terminal cells produce 1–2 spermatangia; involucral cells absent. Tetrasporangia occur on numerous whorls of minute fascicles clustered in constrictions of cells near the thallus apex, inner fascicles consisting of short pedicels 40–50 µm long bearing a whorl of 3–7 lachrimiform tetrasporangia 55–67 µm in diameter, produced successively, and tetrahedrally divided; outermost fascicles also each bearing 1(–2) inflated, incurved 1-celled involucral branches, 110–180 µm in diameter and L/D 1.5–2, forming a composite palisade-like involucre about clusters.

Distribution.Swan River, W. Aust., to Tas. India and St Paul I., Indian Ocean.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 328–329 (1998)]