Macromitrium brevicaule (Besch.) Broth.

Thouvenot, Louis, 2019, A review of the genus Macromitrium Brid. (Orthotrichaceae, Bryophyta) in New Caledonia, Cryptogamie, Bryologie 20 (16), pp. 167-217 : 178-180

Macromitrium brevicaule (Besch.) Broth.

Naturlichen Pflanzenfamilien I (3): 486 (1903).

Micromitrium brevicaule Besch., Annales des Sciences naturelles, botanique, sér. 5, 18: 211 (1873). — Type: New Caledonia. Balade, Vieillard 1734 (Lecto-, BM [ Vitt & Ramsay 1985a]; iso-, PC[PC0096499, PC0108104]!). — Macromitrium brevicaule var. latifolium Broth. et Paris , nom. herb. — Type: New Caledonia, “Insula pinorum, cataractorum Koumania”, 1909, Le Rat s.n. (Reference specimen: PC0096523! pro parte).

ILLUSTRATIONS AND DESCRIPTION. — As Macromitrium wattsii : Vitt (1983).

DISTRIBUTION IN NEW CALEDONIA. — This lowland species was collected between 0-55 m a.s.l. in North Province (type locality), South Province main island and Île des Pins.

TOTAL RANGE. — Australasia.

SELECTED SPECIMENS. — New Caledonia. Province sud, Nouméa, Tina, 24.IX.2012, on calcareous rock in mangrove, 0 m, Thouvenot NC898, on bark in dry forest, 5 m, Larraín 35301; J.-M. Tjibaou Center, 24.IX.2012, mangrove, 0 m, Thouvenot NC900; Yaté, St Gabriel, 22.IX.2008, on Pandanus roots in coral islet, 2 m, Thouvenot NC93 (PC); Bourail, Gouaro-Deva, 25.IX.2008, on bark in riparian forest, 55 m, Thouvenot NC1121; on bark in coastal forest, 2 m, Thouvenot NC1126 (PC); Île des Pins, Kuto, 30.XII.2010, Guionnet NC505.

DESCRIPTION

Pseudautoicous

Plant

Small, dark green, creeping stems with dense short branches, (1.5-) 3-4 mm long.

Branches

When dry with leaves tightly spirally coiled, carinate with conspicuous white costae, erect-spreading when moist.

Branch leaves

Lingulate, short and wide, 1-1.4 mm long, 0.3-0.5 mm wide, L/l = c. 3, apex obtuse to slightly retuse, mucronate, costae thick, strongly prominent at back, excurrent in a mucro.

Upper cells

Single-layered, small, 7-8(-10) µm wide, rounded-quadrate, bulging, thick walled, with several small papillae, evenly ranked, marginal cells smoother and clearer in one rank, intermediate cells few, quadrate to oblong, very thick walled, lumina rounded to elliptic, smooth, lower cells very few, rectangular, 7-20 µm long, 7-10 µm wide, less thick walled, smooth.

Fusiform gemmae

Present on leaves.

Perichaetial leaves

Similar to the vegetative ones.

Calyptrae

Naked, margin laciniate. Setae short, 5 mm long, thick, straight to flexuous, vaginulae naked or nearly so.

Capsules

Oblong-elliptic, 2 mm long, with 8 ribs on the small rim.

Peristome

Single.

REMARKS

Macromitrium brevicaule is easily identified when propagules are seen. In addition, it may be separated from other small species with small setae and short and few basal cells by: 1) the linguiform short leaves with wide obtuse to truncate apex; 2) the smooth basal cells; 3) the naked calyptrae; and 4) its ecology: M. brevicaule grows at the lowest altitudes, often in mangrove or dry forest, in coastal saltwater environment or riparian forest.

With hand lens, sterile dry plants might be confused with Macromitrium tongense which has similar short branches with tightly spirally arranged leaves, but isolated leaves have another shape and microscopical examination shows the multi-layered upper areolation and the papillose lower cells of the latter.

The specimen of PC labelled Macromitrium brevicaule var. latifolium contains a large part of M. tongense and a small part of M. brevicaule . A new specimen recently collected in 2012 in Île des Pins corresponds to this plant which do not differ from the type.