Grimmia laevigata (Brid.) Brid.

Eva Maier, Michelle J. Price & Terry A. Hedderson, 2017, A revision of Grimmia (Grimmiaceae) from South Africa and Lesotho, Candollea 72 (1), pp. 199-230 : 213-215

6. Grimmia laevigata (Brid.) Brid.

, Bryol. Univ. 1: 183. 1826

( Fig. 8 ).

[ Campylopus laevigatus Brid., Muscol. Recent. Suppl. 4: 76. 1819.

Lectotypus (designated by Cao & Vitt, 1986: 181): itAly: sine loc., s.d., Anon. s.n. ( B!).

5 Grimmia senilis Shaw in Cape Monthly Mag. 17: 380. 1878.

Typus: South AfriCA. Prov. Cape: Dry karroo dyke on bare rock , Longhope Cookhouse , 900 m, IV.1921, Sim 9956 (holo-: PRE!), synonymized by Magill (1981: 277).

Gametophyte. Dioicous. Female: innermost perichaetial leaf up to 2 mm long, sheathing up to broadest part of leaf, narrowed at leaf base, ovate to broad-ovate, lower half hyaline or only some rows of hyaline cells at margin, vanishing at mid-leaf, costa obscure in apical part, excurrent in long, denticulate hair-point; perigonia as multifoliose buds at tips of branches; male: innermost perigonial leaf up to 1 mm long, sheathing, broad-ovate, suddenly narrowed to acute apex with hyline cell, hyaline in lower part, costa vanishing below apex, paraphyses short, numerous. Growth form: cushion lax, young shoots mostly present, originating from decomposing plants, with scale-like leaflets appressed to stem, costa vanishing below acute apex, with sharply pointed hyaline cell or short hair-point; plants erect, scarcely branched, slightly radiculose at base, stems up to 20 mm high, central strand welldeveloped. Leaves in lower part of stem scale-like, becoming gradually longer to tip of stem, 1.2-1.8 mm long, rarely up to 3 mm long, imbricate, appressed to stem when dry, older leaves bending backwards when moistened, younger leaves moving slightly, erect or spreading when wet; from short (~1/5 of leaf length), rounded, half-sheathing, slightly decurrent leaf base, lingulate or broad-lanceolate, tapering to obtuse or rounded, even acute apex, hair-point roughly denticulate, occasionally nearly smooth; leaf form in situ, widely concave or concave throughout, margin plane; some rows of basal paracostal cells rectangular, walls smooth or faintly nodulose, towards margin in sheathing part cells isodiametric or transversely rectangular or oval, transverse walls thicker than longitudinal walls, in laminal part cells homogeneous, rounded, walls thick; leaf base, seen in transverse section, unistratose, in transitional part bistratose in places, in laminal part bi- to tristratose, at margin from insertion up to apical part one or more cell rows unistratose, in apical part at least one side unistratose, at apex bistratose. Costa, seen on dorsal side, at leaf base large, from above widest part of leaf up to apex indistinct, excurrent, in laminal part dorsal cells not different from lamina cells, seen in transverse section, on dorsal side at insertion and lower part of leaf flat, weakly convex, at upper part slightly rounded, on ventral side at leaf base widely channelled, in upper part narrowly so, at insertion and leaf base from 7 to 11 ventral cells, most of them guide cells, a small median band of substereids, interrupted by 3 groups or one large central group of hydroids, substereids and hydroids vanishing in apical part, in transitional part number of guide-cells reduced to 4, in laminal part with 2 guide cells, sunken into narrow channel, adaxial cell walls strongly thickened.

Sporophyte. Seta up to 3 mm long, straight, vaginula 1 mm long, cylindrical. Capsule emergent, obloid, smooth, exothecial cells elongated, of variable shape, slightly curvilinear, stomata in short neck, annulus of three rows of cells, detaching spirally in groups. Calyptra mitrate, in upper part brownish, lobed, covering upper part of capsule. Operculum conical, beak straight, blunt, margin uneven or crenulate, one or two marginal rows of rounded cells, in conical part irregular, walls thickened, curvilinear, faintly nodulose. Peristome teeth erect when dry, broad at base, slit half way down to two or three branches or perforate, lower dorsal side smooth, upper dorsal and ventral sides sparingly to densely covered with rounded papillae, trabeculae broad, distant, protruding, in upper third thin. Mature IX. Spores 12-16 µm, smooth.

Diagnostic characters. – Gametophyte. Leaves scale-like on young shoots and from lower part of stem with short hairpoint or at least with a sharp hyaline end cell ( Figs. 8 B-D); base of stem leaves short, rounded, half-sheathing, at margin from insertion up to apical part one or more unistratose cell rows. Costa with hydroids, in upper part of leaf with 2 guide cells sunken into a narrow channel, their adaxial cell walls strongly thickened ( Fig. 8 H), a specific character of G. laevigata . Sporophyte. Peristome teeth slit or perforated.

Distribution, habitat and ecology. – Grimmia laevigata is widespread across temperate areas of the globe, with extensions into the tropics, and it occurs on all continents except Antarctica. This species is very common in arid and semi-arid zones, and especially in regions with a Mediterranean-type climate. In Africa it is common across the desert and semi-desert areas, and also occurs on higher summits in tropical regions, but it is apparently absent from west- and central-tropical Africa.

In South Africa and Lesotho, G. laevigata , along with G. pulvinata , is one of the most widespread species in the study area where it has been recorded from all the major biomes ( Fig. 1 F). It is especially common on shale substrates throughout the various types of karoo vegetation, occurring from 80 m to 2,250 m.

Notes. – A total of 133 specimens were seen. Of these 16 had sporophytes, 5 of which had capsules that were in good condition. The leaf form and length are very variable, the hairpoint is short or elongate, sharply and densely denticulate, rarely nearly smooth. The normally bi-stratose lamina may show partially tristratose patches. In rare cases the costa may be overlaid ventrally by supplementary cells on one side or both sides of the leaf axis, thus covering the guide cells.

A specimen of G. laevigata that is cited in Dixon & Gepp (1923) is housed in PRE as “G. campestris Burchell [ex Hook.], no. 135, coll. Rehmann, Cape Town, s.d.”.

Selected specimens examined. – South AfriCA. Prov. Northern Cape: Namaqualand, Richtersveld Mountains , Khubus , narrow valley running east of town below Vandersterrberg, 28°25’09”S 17°02’38”E, up to c. 800 m, 23.IV.2000, Hedderson 13219 ( BOL, G). Prov. Western Cape: Koue Bokkeveld Mountains , Twee Riviere , Suikerbossie Farm , c. 900 m, 32°40’30”S 19°16’02”E, 7.IV.2001, Hedderson 13782 ( BOL); c. 6 km von Clanwilliam dam , c. 200 m, 7.IX.1990, Lübenau SA 62 ( G, STU).

Figures

Fig. 1. – Species richness (A) and geographic distribution (B-F) of Grimmia Hedw. species in South Africa and Lesotho. A. Distribution of species richness in the genus Grimmia Hedw. at the Quarter-Degree Square (QDS) scale; B. Grimmia consobrina Müll. Hal.; C. Grimmia donniana Sm. (stars) and G. elongata Kaulf. (circles); D. Grimmia fuscolutea Hook.; E. Grimmia kidderi James; F. Grimmia laevigata (Brid.) Brid.

Fig. 8. – Grimmia laevigata (Brid.) Brid. A. Transverse section of stem; B, C. Leaves; D. Outlines of transverse section of leaf; E. Cells in leaf base; F, G. Transverse sections of leaves. [A, C, D-F: Hedderson 13782, BOL; B: Hedderson 13219, BOL; C, G: Lübenau SA 62, STU]