Haplomitrium monoicum J.J.Engel

Thouvenot, Louis & Müller, Frank, 2021, Contribution to the bryophyte flora of New Caledonia IV. Species new to the country, new localities together with taxonomic notes, Cryptogamie, Bryologie 20 (13), pp. 181-196 : 183-184

Haplomitrium monoicum J.J.Engel

SPECIMENS EXAMINED. — New Caledonia. South Province, Yaté, Chakéké lake, 22°6’29”S, 166°54’29”E, on bare soil on the banks of a dry creek,alt. 402 m, 4.X.2019, Thouvenot NC2587 PC[(PC0699830)], NC2588 (herb. Thouvenot); 22°5’58”S, 166°54’44”E, small dry creek, 4.X.2019, Laudereau NC2589 (herb. Thouvenot).

COMMENTS

This New Caledonian endemic was only known from the type locality in Montagne des Sources ( Engel 1981, Bartholomew-Began 1991) and its sporophyte was unknown. The two nearby new localities at Yaté, also in South Province, show similar ecological features but at lower elevation (400 m vs 950 m) and fertile plants allow us to describe the sporophyte after the specimen Thouvenot NC2588. The specimens from Chakéké Lake are well characterized being the only monoicous species in the genus and the fertile specimen contains shoots of both sexes arising from the same rhizome, antheridia whitish, dehisced, subsessile, 2(-3) grouped at the axil of leaves in the upper part of the shoot, but not terminal, archegonia reddish-brown, located like the antheridia, fertilized gynoecia developing long cylindrical calyptra, 3 mm long. More distinctive features were observed: 1) smaller size; 2) erect leafy shoots simple, up to 7 mm high; 3) conspicuous leaf border of 1(-2) cells thicker-walled and somewhat larger than the submarginal ones; and 4) median cells large, (35-55) × (60-75) µm, 5) leaf base area bistratose up to ¼ the leaf length.

Sporophyte ( Fig. 2 )

Long exserted, about twice the calyptra length, seta 6-7 mm long, capsule sublinear, 2.5 mm long, 0.3 mm wide, cells long rectangular, with a single longitudinal thickening. Elaters and spores not seen.

The plants were growing scattered on ultramafic bare soil on the banks of intermittent creeks, shaded by small trees of a gallery forest inside a shrubland typical of the large South Caledonian ultramafic massif. The species still can be viewed as endemic to this massif.

Figures

FIG. 2. — Haplomitrium monoicum J.J.Engel: A, female shoot with sporophyte; B, dehiscent capsule; C, capsule wall cells. All from Thouvenot NC2588. Scale bars: A, 1 mm; B, 0.5 mm; C, 20 µm.