72. SARCONEURUM Plate 103.

Sarconeurum Bryhn, Nyt Mag. Naturvid. 40: 204, 1902. Type: Sarconeurum antarctium Bryhn.

Plants forming dense cushions, blackish green above, reddish brown below. Stems often branching, to 3 cm in length, rounded-pentagonal in transverse section, central strand absent to strong, sclerodermis absent, hyalodermis indistinct; axillary hairs of ca. 10 cells, the basal 2–3 firm-walled, yellow. Leaves appressed-incurved when dry, spreading-recurved when moist, ligulate-lanceolate, to 1.5 µm in length, broadly channeled across the ventral surface; margins plane, entire; lamina constricted below apex, which ends in a deciduous, cylindrical, sharply apiculate propagulum; base scarcely differentiated in shape to ovate; costa running into the apical propagulum, epidermal cells quadrate to short-rectangular on both leaf surfaces, ca. 4 rows of cells across costa ventrally at midleaf, in transverse section with one stereid or substereid band dorsally (this generally lacking in small leaves), 2–3 guide cells in 1(–2) layers, hydroid strand usually present, a ventral stereid band occasionally present near the leaf base in large leaves, epidermis present ventrally, absent dorsally; upper laminal cells quadrate to rectangular, often transversely elongated, especially along the margins, 15–20 µm wide, 1–2:1, walls evenly thickened or collenchymatous, superficially flattened, papillae low, small, punctiform or bifid, apparently solid, several per lumen; basal cells differentiated medially, thin-walled, bulging-rectangular, to 23 µm in width, 3–5:1. Sexual organs and sporophyte unknown. Laminal KOH color reaction red.

Found on sandy and volcanic soil or on lava at low elevations in Antarctica, and, rarely, southernmost South America.

A report (Matteri 1982) of sporophytes of Sarconeurum glaciale is based on specimens (Argentina: trunks of Nothofagus, TBPA B109, TBPA 3486, BA!) that can be referred to Tortula pygmaea Dix., which is a good species (BM! and see Lightowlers 1985b) found in southern South America and New Zealand. Greene (1975) reported Sarconeurum from South America apparently from specimens of T. pygmaea, a species curiously similar to S. glaciale in general habit and the constricted leaf apex bearing a deciduous, sharply apiculate propagulum (Pl. 103, f. 3–6), but differs in the smaller (ca. 10 µm in width) leaf cells with large, solid bifid papillae and the deep medial groove along the ventral surface of the costa. On the other hand, Lightowlers (1985b) demonstrated that the type (“Fuegia septentrionalis”) of the South American T. lithophila at S is actually S. glaciale.

Sarconeurum tortelloides has been transferred to Tortella, leaving Sarconeurum monotypic.

Hilpert (1933) referred Sarconeurum to the Pottieae near Tortula (without further discussion) but probably because of the generally single stereid band in the costa (Pl. 103, f. 8–10) and the large upper laminal cells. There is considerable similarity to Bryoerythrophyllum, however, in the essentially oblong-lanceolate leaf shape, the presence of apical laminal propagulum in the related genus Mironia (but cf. Tortella tortelloides, which has caducous leaf apices), the bifid papillae, the occasional second stereid band, the medially differentiated basal cells (Pl. 103, f. 7) and the red color in KOH. The cladistic analysis places Sarconeurum in the Pottieae (see Cladograms 13 and 14), surprisingly, near Acaulon.

Additional literature: Greene et al. (1970), Savicz-Ljubitzkaja & Smirnova (1961), Zander (1978h), Zander & Hoe (1979).

Number of accepted species: 1.

Species examined: S. glaciale (BM, NY, US).