Macromitrium aurescens var. caledonicum (Thér.) Thouvenot 2019

Thouvenot, Louis, 2019, A review of the genus Macromitrium Brid. (Orthotrichaceae, Bryophyta) in New Caledonia, Cryptogamie, Bryologie 20 (16), pp. 167-217 : 177-178

Macromitrium aurescens var. caledonicum (Thér.) Thouvenot , comb. nov.

( Figs 2I , 5 )

BASIONYM. — Macromitrium cylindromitrium var. caledonicum Thér. , Bulletin de l’Académie Internationale de Géographie Botanique 19: 21 (1909).

TYPE. — New Caledonia. Bourail. (lecto-, designated here fide Guo in Sched. [2007]: “Bourail, 1905, Le Rat s.n., comm. Franc”: PC [ PC 0083687]!).

TOTAL RANGE. — Macromitrium aurescens s.l. occurs in Australia and New Caledonia. The variety caledonicum is known only from the type locality in South Province of New Caledonia.

DESCRIPTION

Sexual condition

Unknown, the type variety is pseudautoicous according to Vitt & Ramsay (1985a).

Plant

Small, creeping stems with short branches up to 3-5 (-10) mm long.

Branches

When dry with leaves obliquely appressed, spirally coiled around the axis, strong costae prominent at back, when moist erect to slightly patent.

Branch leaves

1.6-1.8 mm long, 0.35-0.55 mm wide, ligulate to oval-lanceolate, strongly carinate in lower part, apex obtuse mucronate, costae thick, ending just below the apex to short excurrent.

Upper cells

Single-layered, 10-12 µm wide, isodiametric, rounded, bulging, with a few small papillae, intermediate cells quadrate to short rectangular, with a single conical papilla, lower cells in a few basal ranks filling less than 1/10 length of the leaf,

20-30 µm long, 10-12 µm wide, short rectangular with thicker porous walls and unevenly sinuous lumina, some with a single high papilla.

Perichaetial

Leaves more or less similar to the vegetative ones.

Calyptrae

Narrowly cylindrical, 3-5 mm long, hairy.

Setae

Short, 5 mm long, straight to slightly curved, vaginulae with long hairs.

Capsules

Narrowly cylindrical, 2 mm long, with irregularly or not plicate rim, peristome not seen in New Caledonian specimen.

REMARKS

In the diagnosis, Thériot (1909) emphasize the leaf length of the New Caledonian plants as the only difference with the Australian Macromitrium cylindromitrium Müll.Hal. currently synonym of M. aurescens Hampe , whose leaf lengths range from 2 to 2.6 mm ( Vitt & Ramsay 1985a). Due to the scarcity of New Caledonian specimens, we cannot decide if the status of variety is valid or not for this plant. But it is likely synonym of the type variety. In addition, ecological requirements seem more or less similar; the type locality of the variety caledonicum, Bourail , is situated at low elevation in the south western plain, the driest part of the island, where Melaleuca quinquenervia and Casuarina collina forests are abundant, while the type variety, a north eastern Australia endemic, is found on barks of Melaleuca , Grevillea and Casuarina at low elevation ( Vitt & Ramsay 1985a).

Macromitrium aurescens and its variety share with a handful of species, namely M. brachypodium , M. brevicaule , M. francii , M. orthostichum , some typical features as: 1) short branches; 2) short setae; 3) leaves ligulate or oval-lanceolate, short to medium sized; 4) upper cells strongly papillose; and 5) basal cells few, short or long, with a few high single papillae. It differs from everyone by having a narrow cylindrical urn, 2 mm long and sub-conduplicate leaves ending in hooked, cucullate apices. When dry, leaves are spirally whorled around the branches.

The latter character is shared with Macromitrium brevicaule which is smaller, has lingulate leaves with fusiform gemmae and naked calytrae.

In addition, Macromitrium brachypodium and M. francii have shorter setae.

Macromitrium orthostichum is distinct by its stout and prorate setae.

Figures

FIG. 2. — Dry branch habits of Macromitrium (II) A, M. sarasinii Thér.; B, M.humboldtense Thouvenot & Franck Müll.; C, F, M. panduraefolium Thouvenot; D, M. larrainii Thouvenot & K.T.Yong; E, M. tongense Sull.; G, M. subvillosum Broth. & Paris; H, M. rufipilum Cardot; I, M. aurescens var. caledonicum (Thér.) Thouvenot. From type specimens (A-D, F, H, I), from specimens Müller NC755 (E), NC764 (G). Scale bars: 1 mm.

FIG. 5. — Macromitrium aurescens var. caledonicum (Thér.) Thouvenot: A, dry branch with sporophyte; B-D, branch leaves; E, intermediate cells in side view; F, branch leaf apex; G, transitional cells; H, upper cells in surface view; I, transverse section in top quarter of branch leaf (fragment); J, basal cells. All drawn from the lectotype. Scale bars: A, 1 mm; B-D, 500 µm; E, G, H, J, 10 µm; F, 100 µm; I, 20 µm.