Macromitrium renauldii Thér.

Thouvenot, Louis, 2019, A review of the genus Macromitrium Brid. (Orthotrichaceae, Bryophyta) in New Caledonia, Cryptogamie, Bryologie 20 (16), pp. 167-217 : 204-206

Macromitrium renauldii Thér.

( Fig. 19 )

Bulletin de l’Académie internationale de Géographie botanique 17:

307 (1907).

Macromitrium gracilipes Cardot, Bull. Herb. Boiss. Sér 2, 8: 168 (1908). — Type: New Caledonia, Balade, Vieillard 1735 (lecto-, designated here fide Guo in Sched. [2007] PC[PC0083666]!; isolecto-, PC[PC083665]!) syn. nov.

Macromitrium leratioides Broth. & Paris, Öfversigt af Finska Vetenskaps-Societetens Förhandlingar 51A (17): 15 (1909). — Type: New Caledonia, Mt Dzumac, “ad arbores”, A. Le Rat s.n. (lecto-, designated here fide Vitt in Sched. [1983]: H.BR[H.BR2618013]!; isolecto-, PC[PC0096518]! pro parte) syn. nov.

TYPE. — New Caledonia. “env. Nouméa”, Franc s.n. (lecto-, designated here, fide Guo in Sched. [2007] PC [ PC 0083728]!).

DISTRIBUTION IN NEW CALEDONIA. — More frequent in South Province. In North Province known only from the type specimen.

TOTAL RANGE. — Endemic to New Caledonia.

SELECTED SPECIMENS. — Macromitrium renauldii New Caledonia. Province Sud, Païta, Dzumac, on bark in mountain forest with Cyperaceae , 915 m, 18.IX.2008, Thouvenot NC196; Boulouparis, Mt Do, on bark in mountain wet forest, 800m, 25.X.2012, Thouvenot NC1017 (PC); Yaté, Madeleine waterfalls, epiphyt, 248 m, 4.IX.2003, Frank Müller NC761 (DR); Plaine des Lacs, on bark of Retrophyllum min or on river bank, 245 m, 6.X.2016, Thouvenot NC2367 (PC), Parc de la Rivière Bleue, on bark in wet forest on deep soil, 175 m, 5.X.2016, Thouvenot NC2233; Plaine des Lacs, Creek Amos, on bark in gallery forest inside shrubland, 270 m, 6.X.2016, Thouvenot NC2377 (PC); Pic du Grand Kaori, on bark in shrubland, 490 m, 4.X.2016, Thouvenot NC2263. M. leratioides ; Plaine des Lacs, 1904 (?), Compton s.n. (PC009650).

DESCRIPTION

Pseudautoicous

Dwarf male plants on leaf axis of female branches.

Plant

Small to medium sized, upper parts yellow-green, older lower parts brown or olive green, creeping stems densely branched.

Branches

Thin, short to medium, 2-8(-10) mm long, 0.8-1 mm wide, straight, simple or rarely shortly furcate, when dry loosely coiled, leaves loosely erect or obliquely to transversely oriented, individually twisted, carinate, the apex incurved to circinate, unevenly directed, when moist erect to patent, usually little recurved.

Branch leaves

Small to medium, 0.8-1.8(-2.3) mm long, 0.2-0.4 mm wide, lanceolate, more or less long acuminate, translucent thorough, basal part being 1/3 the leaf length, apex acute, apiculate to very short aristate, aristae less than 0.1 mm long, costae thick, ending just below the apex to excurrent, margins smooth, plane to slightly recurved on one side near base.

Upper cells

Single-layered, small, 7-10(-12) µm wide, very thick walled, quadrate with rounded to oval lumina, flat to little bulging, smooth or rarely with a few low papillae, the cells arranged in continuous longitudinal rows with the transverse limits usually inconspicuous, marginal cells sometimes smaller in 1-3 ranks, transitional part null to very short, with an inverted “v” shape, transitional cells short rectangular, thick walled, sometimes with single rounded papillae, lower cells rectangular elongate, 10-40 µm long, 7-10 µm wide, very thick walled, walls 2-5 µm wide, lumina straight to wavy, narrow, single papillae scarce to numerous, possibly displayed on plicae, low to high rounded.

Perichaetia

More or less obvious, loosely erect, not sheathing, perichaetial leaves usually distinct, larger than the vegetative ones, oblong to more widely lanceolate or triangulate.

Calyptrae

Hairy.

Setae

Medium to large, 12-25 mm long, thin, straight to flexuous, vaginulae with long hairs, usually conspicuous.

Capsules

1.5-2 mm long, narrowly elliptic to sub-cylindric, smooth, rims brown, small, erect, without plicae.

Peristomes

Present, single or little developed.

REMARKS

The taxa brought together under the name of M. renauldii share: 1) the original arrangement of the smooth upper cells in very regular longitudinal rows, underlined by thicker walls; 2) short branches; 3) branch leaves when dry typically spirally coiled with apices incurved like crooks or circinate; 4) basal cells elongate with narrow lumina usually wavy and single papillae; 5) long setae; and 6) vaginulae and calyptrae hairy. In the upper cells, the border of contiguous transversal walls of cells are barely visible and the bands of cells appears in parallel files more or less transversally staggered, making the lamina rough. The lower cells are also arranged in longitudinal rows, underlined by thicker longitudinal walls and sinuous lumina which make a conspicuous wavy line. So that the entire leaves appear longitudinally striated. The ornamentation of the lower parts is variable, from nearly smooth thorough to locally strongly papillose. The variability concerns the branch length and shape or the costa excurrence. The characteristic features underlined in the diagnosis are incompletely recognized in the type specimens examined: in M. gracilipes, Cardot (1908) emphasises shorter branches, branch leaves patent-spreading when moist, less excurrent costae and smooth capsule rims versus squarrose leaves when moist with long excurrent costae and plicate capsule rims in M. renauldii . The type specimen checked exhibits less evidence because the leaf apices are varying in shape and costa excurrence. In the Brotherus’ description of M. leratioides (1909), all the features are identical to those described by Thériot (1907) for M. renauldii and observed in the type. The type specimens of the three taxa and nine recently collected samples match our description with emphasis on branch leaf shapes, cell ornamentation and areolation, seta length, branch density, length range and shape in dry condition.

Macromitrium taoense shares the same areolation, setae and branch length and branch habit in dry condition but differs from by its naked calyptrae and vaginulae. However, it could be reduced to synonymy, but material of M. taoense is too scarce to conclude.

Thus defined, M. renauldii is found on barks of trees and treelets in riparian shrublands, lowland mesophilous forests or mountain wet forests with fairy open canopy, in the ultramafic massifs. It is a little frequent species growing in lowland up to medium elevation, usually collected between 100-1000 m a.s.l.

Figures

FIG. 19. — Macromitrium renauldii Thér.: A, G, capsules; B-F, O, branch leaves; H, transverse section in basal quarter of branch leaf; I, transverse section in top quarter; J, branch leaf apex; K, basal cells; L, upper cells; M, perichaetial leaf; N, sporophyte. Drawn from the lectotype (C-E, J-L), from the lectotype of M. leratioides Broth. & Paris (A, F), from the lectotype of M. gracilipes Cardot (O), from the specimens Thouvenot NC2263 (B), NC2229 (G), NC2377 (H, I), NC2233 (M), NC1017 (N). Scale bars: A, G, 1 mm; B-F, M, O, 1 mm; H, I, 20 µm; J, 100 µm; K, L, 10 µm; N, 1 mm.