Semnocarpa minuta Huisman, Foard & Kraft

Scientific Description

Habit and structure. Thallus 1–10(–30) mm high, with one to several simple or branched terete axes, elongate-clavate and saccate, branches ovoid to clavate, basally constricted, apices rounded; axes and branches 0.5–1 mm in diameter. Holdfast monostromatic, 0.3–0.8 mm across; epiphytic on various algae. Structure multiaxial, with a group of short apical filaments producing the network of medullary filaments bearing secretory cells and cutting off outwardly the layer of large, ovoid, inner medullary cells 20–35 µm in diameter and an outer cortex 1–2 cells thick of small ovoid cells 4–6 µm in diameter. Holdfast cells ovoid, 8–12 µm in diameter. Rhodoplasts discoid, in chains in inner cells.

Reproduction. Gametangial thalli dioecious. Carpogonial branches 3-celled, borne on inner cortical cells together with a 2-celled auxiliary cell branch, auxiliary cell with a proteinaceous globule. Carposporophyte developing within the branch cavity, producing several lobes with all cells forming ovoid carposporangia 8–12 µm in diameter, surrounded by an involucre of relatively coarse filaments connected to the auxiliary cell initial and adjacent cortical filaments. Cystocarps completely immersed, projecting into the cavity, with a small cortical ostiole. Spermatangia in sori near the branch apices, cut off from initials on the outer cortical cells, elongate-ovoid, 3–6 µm in diameter. Tetrasporangia in depressed sori, cut off thallus inwardly from cortical cells lining the depression, subspherical to ovoid, 120–135 µm in diameter, tetrahedrally divided.

Distribution.Port Denison, W. Aust., to Margaret Brock Reef, Cape Jaffa, S. Aust., and Eaglehawk Neck, Tas. Probably more widely distributed but easily overlooked.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIB: 144–146 (1996)]