Synonyms: (basyonim) Melobesia lejolisii Rosanoff pro parte (1866) p. 62; Dermatolithon lejolisii (Rosanoff) Foslie (1898) (3) p. 11; Melobesia lejolisii f. typica Foslie (1905) (3) p. 102; Heteroderma lejolisii (Rosanoff) Foslie (1909) (2) p. 56; Melobesia microspora Rosenvige (1917) p. 256; Fosliella lejolisii Howe (1920) p. 588; Pneophyllum microsporum (Rosenvige) Chamberlain (1983) p. 395; Pneophyllum lejolisii (Rosanoff) Chamberlain (1983) p. 359.

VEGETATIVE FEATURES

Thallus habit : encrusting, flattened (A), without excrescences with more or less smooth surface. Margin grown thin (anastomosing with other margins belonging to adjacent thalli); having frayed edges. Size: 0.5mm diameter (young thallus), 2-5mm diameter (in old coalescent thalli, 0.06-0.1mm thick). Colour of living specimen: pink, red or violet. Colour of dried specimen: mauve grey.

Unistratose thallus (multilayered, 2-4 layer, only around conceptacles), thickness 30-90µm. Basal filaments: straight, squarish or slightly rectangular cells: 6-9 (15)µm long x 6-l0µm diameter, arranged in divergent rows. Epithallial cells: oval, rounded, not flared, partially covering a cell below to which they are smaller. Cell connections: cell fusions (very numerous). Other features: intercalary trichocytes rare, not well developed, colourless, among filaments of pigmented cells (A).

Gametangial conceptacles and tetra/bisporangial conceptacles: uniporate, slightly raised with flat roof, convex, numerous and grouped, immersed or raised respect to surface; 54-130µm diameter x 30-70µm high. Canal pore surrounded by not specialized cells (C). Other features: spore germination disc of 12 central cells (B), surrounded by a ridge of cells from which basal filaments branch off  radially. Phenology: from February to June.

Habitat: epiphytic on seagrasses leaves (Zostera, Posidonia, Rupia, Cymodocea) and rarely on other algal species (Flabellia, Halimeda). Bathymetric distribution: littoral. Geographic distribution (Babbini & Bressan 1997):

Alboran Sea (A): Morocco; Western Mediterranean Sea (African shores) (B): Algeria; Middle Western Mediterranean Sea  (C): Spain, France, Italy; North Western Mediterranean Sea  (D): Spain, France, Italy; North Adriatic Sea (E): Italy, Slovenia, Croatia; Middle Adriatic Sea (F): Italy, Croatia; South Adriatic Sea (G): Italy; South Eastern Mediterranean Sea (H): Italy, Malta, Tunisia, Libya; Middle Eastern Mediterranean Sea (L): Greece, Turkey, Syria; North Eastern Mediterranean Sea (M): Greece, Turkey.