Dicroglossum crispatulum (Harv.) A.Millar & Huisman

Scientific Description

Habit and structure. Thallus erect, medium red, 2–4 cm high, complanately branched with subdichotomous branches 1–3(–5) mm broad, margins straight to strongly crispate, with a central midrib (no microscopical veins), blades monostromatic. Holdfast small, discoid, stoloniferous; usually epiphytic (on Amphibolis and various algae). Structure. Apical cell transversely ovoid to obpyriform, segmenting to give axial cells and lateral pericentral cells which produce second-order rows, with only some cells producing third-order rows; most (but not all) rows reach the blade margin; the transverse pericentral cells remain undivided. Branching at the apex is exogenous (or marginal) with a lateral pericentral cell forming a third-order row which develops as a new apex, thus forming a subdichotomy which is shown by branching of the midrib in lower parts. Cortication of the midrib occurs by slender rhizoidal filaments, spreading to the adjacent wings on older thalli. Cells probably multinucleate; rhodoplasts discoid.

Reproduction.Reproductive structures are borne both on the blades and on small determinate bladelets arising from the central axial cells. Gametophytes dioecious. Procarps occur on the transverse pericentral cells on both sides of the blades, in series on consecutive segments, each with two 4-celled carpogonial branches and one sterile group. Carposporophyte with a branched basal fusion cell and short terminal chains of subspherical to ovoid carposporangia 12–25 µm in diameter. Cystocarps sunken within the blades, ostiolate; pericarp 3–4 cells thick. Spermatangial sori on both sides of the blades and the midrib, elongate, with the primary cells cutting off initials which each produce several anticlinally elongate spermatangia. Tetrasporangial sori produced mostly on determinate bladelets from the midrib, the sorus covering the central blade but with a sterile margin; tetrasporangia cut off from cortical cells arising from the primary cells, in 2 layers in cross section, covered by smaller outer cortical cells, subspherical, 35–50 µm in diameter.

Distribution.Fremantle, W. Aust., to Vivonne Bay, Kangaroo I., S. Aust.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 30–32 (2003)]