Grimmia sessitana De Not. A. Transverse 1869
Creators: name: Eva Maier
name: Michelle J. Price
name: Terry A. Hedderson
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Plantae
Bryophyta
Bryopsida
Grimmiales
Grimmiaceae
Grimmia
Grimmia sessitana

description: 12. Grimmia sessitana De Not
. in Atti Reale Univ. Genova 1: 704. 1869
(Fig. 14).
Lectotypus (designated by Cao & Vitt, 1986: 164): itAly: “Frane alle scaturigini del Vogna, sotto l’ospicio della Valdobbia, in Val Sesia”, s.d., Carestia 55 (RO; isolecto-: G [G00052457]!).
Gametophyte. Monoicous, occasionally dioicous. Female: innermost perichaetial leaf sheathing, 2.6-2.8 mm long, concave; male: perigonia as buds on short stalks on branches of female plants, terminal or in leaf axils, several on one plant. Growth form: cushions dense, compact, adherent to substrate with rhizoids, stems to 20 mm high, plants erect, radiculose at base, strongly branched, central strand developed. Leaves crowded, in lower part of stem to 1.2 mm long, muticous or short hair-point present, becoming gradually longer, to 2.4 mm long, loosely arranged on stem, apices flexuose when dry, rapidly bending backwards when moistened, quickly moving to erect or erecto-patent position when wet, from nearly rectangular or ovate leaf base lanceolate, tapering to acute apex, hair-point nearly smooth; leaf form in situ, at insertion and in leaf base concave, narrowly keeled in laminal part, margin recurved on one side from insertion to broadest part of leaf or plane on both sides; basal paracostal cells in upper stem leaves, elongate-rectangular, walls thin, smooth, cells at margin elongate-rectangular, nearly of the same length as paracostal cells, transverse walls thickened, in lower stem leaves paracostal cells elongate-rectangular, towards margin some rows shortrectangular or quadrate, transverse walls thickened, smooth, all leaves with some hyaline marginal cell rows, vanishing at broadest part of leaf, above broadest part of leaf cells short rectangular to quadrate, lumina rounded, walls smooth or slightly sinuose, in apical part isodiametric, lumina rounded, walls thickened; leaf, seen in transverse section, at base unistratose, laminal part unistratose, bistratose in places or nearly completely bistratose, in surface view seen as striae. Costa, seen on dorsal side, enlarged from above broadest part of leaf to apex, excurrent, seen in transverse section, dorsally rounded, ventrally at insertion and in leaf base channelled, in laminal part narrowly or very narrowly so, at insertion and in leaf base 4 guide cells, in laminal part 2 guide cells, a median group of hydroids present, in upper part of leaf transformed to substereids.
Sporophyte. Seta to 4 mm long, rarely straight mostly slightly inclined, vaginula 0.6 mm long, short cylindrical, with ochrea. Capsule exserted, erect, oblong-ovoid, constricted at capsule mouth after spore release, smooth, exothecial cells mostly hexagonal, elongate, walls thin, seen in transverse section of capsule, exterior walls slightly bulging, stomata at base of capsule, numerous or few, neck lacking, annulus of 3-4 rows of persistent cells, which may detach singly, seen in surface view quadrate to transversely rectangular, lumina large. Calyptra cucullate. Operculum conical, blunt, base uneven, formed by two rows of small, nearly isodiametric cells, in conical part cells irregular, rectangular, isodiametric, lumina rounded. Peristome teeth erect or spreading when dry, lanceolate, entire or perforate, separated down to insertion, lower dorsal side smooth, upper dorsal and ventral sides covered with rough papillae, trabeculae in lower part small, in upper part thin. Spores 8-9 µm, smooth.
Diagnostic characters. – Gametophyte. Upper stem leaves with marginal cells elongate and nearly the same length as paracostal cells, whilst in the base of lower stem leaves the marginal cells are short-rectangular to quadrate. In all leaves cells are smooth with thickened transverse walls, some cell rows are hyaline, vanishing above leaf base. Costa, enlarged from above broadest part of leaf to apex.
Distribution, habitat and ecology. – In the northern hemisphere Grimmia sessitana is widely, but disjunctively, distributed in mountainous regions. It is known from eastern and western North America, Europe, and the high mountains of Asia, including from Japan. In the southern hemisphere it is known only from the study area, New Zealand, the Falkland Islands, the South Shetland Islands and the Queen Mary Coast of Antarctica.
Grimmia sessitana is rare in the study area (Fig. 2 F). It is known from four high altitude (1,670-1,940 m) sites in the mountains of the Western and Northern Cape Provinces, three in the Hex River Mountains and one on the Hantamsberg. In all four localities it grows on more or less sheltered ledges of quartzitic sandstone.
Notes. – Four specimens were seen and all were sterile. Grimmia reflexidens Müll. Hal., a name occasionally used on labels of South African specimens, is not a synonym of G. sessitana. The arguments for the correct use of the name G. sessitana De Not. are given in Maier (2002: 224; 2010: 357).
Selected specimens examined. – South AfriCA. Prov. Cape: Ceres Dist., Roodeberg, Hex River Mts. Shelf at foot of cliffs, S side, 2130 m, 27.XII.1952, Esterhuysen 20971 (BOL); Hantamsberg plateau, near F.M. tower, 3119 BD, 25.IX.1980, Schelpe 8037 (BOL).
description: Published as part of Eva Maier, Michelle J. Price & Terry A. Hedderson, 2017, A revision of Grimmia (Grimmiaceae) from South Africa and Lesotho, pp. 199-230 in Candollea 72 (1) on pages 225-226, DOI: 10.15553/c2017v721a12, http://zenodo.org/record/888344