Metamastophora flabellata (Sond.) Setch.

Scientific Description

Habit and structure. Thallus normally pinkish to dull red, arborescent, mostly 5–23 cm tall, attached by a basal holdfast that produces one to several erect stipes with flattened, branched, ribbon like branches that commonly have vein-like thickenings in older portions; branching mostly in one plane, pseudodichotomous to pseudopolychotomous. Structure pseudoparenchymatous with dorsiventral organisation throughout; construction dimerous, consisting of a single layer of branched, laterally cohering, filaments occurring ventrally in younger portions but internally in older portions, each composed of palisade cells (10–)15–40(–46) µmlong and (30–)35–85 µmhigh, and additionally of epithallial cells or of filaments terminating in epithallial cells and composed of cells that arise dorsally and in older portions ventrally and more or less perpendicularly from most cells of the unistratose palisade layer and are mostly 5–20 µmin diameter and 19–85(–109) µmlong; epithallial cells 11–49 µmin diameter and (8–)11–25 µmlong with distal walls rounded or flattened but not flared; cells of adjacent filaments joined by cell fusions, secondary pit-connections very occasional in older parts of thalli; haustoria unknown; trichocytes uncommon, occurring singly or in horizontal rows or fields.

Reproduction.Vegetative reproduction unknown. Gametangia, carposporangia and tetrasporangia produced in uniporate conceptacles; gametangia and carposporangia formed on thalli separate to those bearing tetrasporangia, conceptacles borne only on dorsal surface of branches. Bisporangia unknown. Gametangial thalli dioecious or rarely monoecious. Carpogonia terminating 2- or 3-celled filaments arising from the female conceptacle chamber floor. Mature female-carposporangial conceptacle roofs normally dome-like, protruding above surrounding thallus surface, 110–160 µm thick, composed of 3–6 layers of cells above the chamber, conceptacle chambers 760–1075 µm in diameter and 145–435 µm high. Carposporophytes developing within female conceptacles after karyogamy, composed of a conspicuous central fusion cell and several-celled gonimoblast filaments bearing terminal carposporangia 110–190 µm in diameter. Spermatangial filaments unbranched, borne across the male conceptacle chamber floor, mature male conceptacle roofs dome-like or more commonly rostrate, protruding above surrounding thallus surface, 370–960 µm thick, composed of 13–26 layers of cells above the chamber, male conceptacle chambers 850–950 µm in diameter and 200–370 µm high excluding the pore canal 900–1500(–2000) µm long. Tetrasporangial conceptacle roofs dome-like, protruding above surrounding surface, 110–260 µm thick above the chamber and composed of 3–7 layers of cells, pore canals lined by cells that are orientated more or less parallel to the roof surface and protrude slightly into the canal, conceptacle chambers 625–900(–1000) µm in diameter and 230–510 µm high; tetrasporangia peripheral to a central columella, each mature sporangium 90–240 µm in diameter and 175–340 µm long, containing zonately arranged tetraspores.

Distribution.Southern Africa. In Australia, Kalbarri, W. Aust., to Waterloo Bay, Wilsons Promontory., Vic., and from Currie, King I., Tas.

Habitat. M. flabellata has been found on rock in intertidal pools and to depths of 48 m in southern Australia.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIB: 243–246 (1996)]