Mastophora pacifica (Heydr.) Foslie

Scientific Description

Habit and structure. Thallus normally pinkish, encrusting to layered or foliose, mostly 15–70 mm across, epigenous and affixed by local cell adhesion or by unicellular rhizoids; lamellate branches applanate and inconspicuous. Structure pseudoparenchymatous with dorsiventral organisation throughout; construction dimerous, consisting of a single ventral layer of branched, laterally cohering, filaments each usually composed of palisade cells 16–32 µm long and 48–80 µm high, and additionally of epithallial cells or occasionally of small groups of filaments terminating in epithallial cells and arising dorsally and more-or-less perpendicularly from cells of the unistratose palisade layer, cells 8–27 µm in diameter and 27–50 µm long; epithallial cells 5–11 µm in diameter and 16–30 µm long with distal walls rounded or flattened but not flared; cells of adjacent filaments joined by cell fusions, secondary pit-connections and haustoria unknown; trichocytes sometimes present, occurring singly or in horizontal rows or fields and occasionally dividing transversely or obliquely to form two cells.

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 thallus surfaces. Bisporangia unknown. Gametangial thalli dioecious. Carpogonia terminating 2- or 3-celled filaments arising from the female conceptacle chamber floor. Mature female-carposporangial conceptacle roofs protruding above surrounding thallus surface, 80–110 µm thick, composed of 2–4 layers of cells above the chamber, conceptacle chambers 555–1330 µm in diameter and 300–520 µm high. Carposporophytes developing within female conceptacles after karyogamy, composed of a conspicuous central fusion cell and several-celled gonimoblast filaments bearing terminal carposporangia 95–215 µm in diameter. Spermatangial filaments unbranched, borne across the male conceptacle chamber floor, mature male conceptacle roofs protruding above surrounding thallus surface, 190–280 µm thick, composed of 5–9 layers of cells above the chamber; male conceptacle chambers 24–375 µm in diameter and 80–125 µm high. Tetrasporangial conceptacle roofs protruding above surrounding surface, 95–190 µm thick above the chamber and composed of (2–)4–8 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 630–835 µm in diameter and 555–630 µm high; tetrasporangia peripheral to a central columella, each sporangium 130–210 µm in diameter and 220–300µm long, containing four zonately arranged tetraspores.

Distribution.China; Vietnam; Indonesia; Guam; Hawaiian I. In Australia, North Point Reef, Rottnest I., W. Aust., to Rye, Vic.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIB: 248–251 (1996)]