Trematodon laetevirens Hakelier

Belkina, Olga A. & Vilnet, Anna A., 2019, Trematodon laetevirens Hakelier & J. - P. Frahm and T. brevicollis Hornsch. (Bruchiaceae, Bryophyta) in Russia, Cryptogamie, Bryologie 20 (19), pp. 247-258 : 251

Trematodon laetevirens Hakelier & J.-P. Frahm

Lindbergia 3: 223 (1976).

DESCRIPTION

Gametophytes

2-3 mm in height;

Leaves

1.0- 1.8 mm long and 0.3-0.6 mm wide, erect spreading or contorted (in Chukotka specimen – leaves slightly falcate and concave), oblong-lanceolate, gradually tapering or on some shoots (in Norwegian, Swedish, Rasvumchorr specimens) rather suddenly narrowed in upper part; leaf margins flat and unistratose, cells in lower part of leaf thin walled, elongate or short-rectangular, 20-60 µm × 12-17 µm, becoming longer and narrower on margins (to 80-100 µm in length) and shorter and quadrate towards the apex (15-35 µm).

Costa

About 100 µm wide (in Norwegian sample – 150 µm, in Kuel’porr – up to 175 µm), occupying¹�₃ of leaf lamina base (in Rasvumchorr sample – some wider, in Chukotka’ – much wider, about ½ of leaf width), ending in and completely filling the apex, without stereids, in cross section with ventral (adaxial) row of large cells, smaller cells on abaxial side and with equal or just smaller “central” cells with curved or even tortuous walls (like after pressing).

Perichaetial leaves

Larger than others, convolute-sheathing, various in shape and size: one of the inner perichaetial leaves conspicuous – much larger and wider (1.8-2.2 mm long × 0.66-0.8 mm wide), straight, oval (or sometimes almost spathulate), rounded off abruptly at the apex (Khibiny, Kamchatka specimens) or with very short obtuse (angle more than 90°) apiculus (Norwegian and Chukotka specimens); one-two other perichaetial leaves also wide, but smaller, with more or less sharp and long apiculus.

Seta

6-7 mm long (to 9-11 mm in Kukisvumchorr and Kuel’porr and 3.5-6.5 mm in Kamchatka and Chukotka).

Capsule

Erect (in Kukisvumchorr specimen slightly inclined), straight (in Swedish sample slightly curved with angle about 160- 170°); capsule neck about equal to the urn in length, about 1.3-1.4 mm long, not strumose, gradually turning into the seta (in Chukotka and Kamchatka specimens the ratio urn – neck is from 1:1.5 to 1: 1.7 in some sporophytes).

Exothecial cells

Rectangular, quadrate or irregular shaped, in indistinct rows (in Kuel’porr arranged in more or less clear rows), with slightly thickened walls (in Norwegian and Swedish specimens – with more thickened walls)

Peristome teeth

All or part of them perforated along the midline (sometimes also on sides) and split at the apex (in Kukisvumchorr and Norwegian specimens – slightly perforated or split).

Annulus

Often partly remaining on the urn mouth, double.

Spores

35-38 µm (in Kukisvumchorr 40-45 µm and in Norwegian sample 40-42 (-45) µm), in Khibiny Mts. maturing in September.