9. EUCLADIUM Plate 10.

Eucladium B.&S. in BSG, Bryol. Eur. 1: 93, 1846 (fasc. 33–36 Mon. 1). Type: Eucladium verticillatum (Brid.) B&S.

Mollia subg. Eucladium (B.&S.) Lindb., Musci Scand. 21, 1879.

Weissia subg. Eucladium (B.&S.) Kindb., Eur. N. Amer. Bryin. 2: 283, 1897.

Weissia sect. Saxicolae Nees & Hornsch., Bryol. Germn. 2(2):P 26, 97, 1831, p.p.

Mollia sect. Eucladium (B.&S.) Braithw., Brit. Moss Fl. 1: 230, 439, 1885.

Weissia sect. Eucladium (B.&S.) Dix., Stud. Handb. Brit. Moss. 210, 1896.

Plants growing in turfs or cushions, bright to dark green above, pale green to yellowish brown below. Stems branching irregularly, 0.5–2.0 cm in length, transverse section elliptical, central strand absent, sclerodermis usually absent, hyalodermis present, inflated; axillary hairs of 5–10 clear cells; occasionally weakly radiculose. Leaves appessed to erect-spreading from base, incurved above when dry, weakly spreading to spreading-recurved when moist, oblong- to linear-lanceolate, 1.5–2.5 mm in length, upper lamina broadly channeled, margins plane, denticulate on lower margins, rarely entire; apex broadly to narrowly acute or subulate; base scarcely differentiated in shape to ovate; costa strong, usually excurrent as a stout mucro, decurrent at base, superficial cells quadrate to elongate ventrally, elongate dorsally, ca. 6 rows of cells across costa ventrally at midleaf, costal transverse section semicircular to elliptical, 2 stereid bands present, epidermis present ventrally, usually present dorsally, guide cells 4–7 in 1(–2) layers, hydroid strand absent; upper laminal cells subquadrate (occasionally rectangular medially), smaller at leaf margins, 8–10 µm in width, 1:1(–2), walls moderately thick-walled, often irregularly thickened, somewhat bulging superficially; papillae low, indistinct, simple to occasionally multifid, scattered to centered, 2–5 per cell; basal cells usually strongly differentiated across leaf or medially, bulging-rectangular to rhomboidal, 12–15 µm in width, 2–5:1, walls hyaline, thin. Dioicous. Perichaetia terminal, inner leaves ovate-lanceolate, to 2.5 mm in length, sheathing, lower cells rhomboidal in lower half. Perigonia terminal, inner leaves long-lanceolate, similar to cauline. Seta ca. 5–6 mm in length, 1 per perichaetium, yellow, twisted little or not at all; theca ca. 1 mm in length, yellow-brown, ovoid to cylindrical, exothecial cells short-rectangular, thin-walled, bulging, stomates phaneropore, present at base of theca, annulus of ca. 2 rows of weakly vesiculose cells; peristome teeth 16, lanceolate, entire to variously cleft, yellow, papillose, rudimentary or to 300 µm, with up to several articulations, straight, basal membrane low, papillose. Operculum conic-rostrate, ca. 0.5–0.8 mm in length, cells in straight rows. Calyptra cucullate, smooth, ca. 2.5 mm in length. Spores 9–14 µm in diameter, pale, essentially smooth. Laminal KOH color reaction yellow. Reported chromosome number n = 13.

Found on calcareous rock in wet places, especially in spray of waterfalls, across Europe and Asia, northern and southern Africa, and North America (including Mexico).

Brotherus (1924–25) accepted the combination Eucladium irroratum (Mitt. in Hook.) Jaeg., as did Dixon (1923). The rigid, erect leaves and the wet, calcareous habitat of this New Zealand species certainly suggest this genus, but technical characters indicate that that species belongs to a monotypic genus, Tetracoscinodon. Eucladium may now be considered a monotypic genus.

The most distinctive characters of Eucladium are the bright green leaves, lack of a stem central strand or sclerodermis and presence of a somewhat inflated hyalodermis (Pl. 10, f. 2), the broad costa, plane leaf margins, which are denticulate below (Pl. 10, f. 6) except in certain Bermuda populations, laminal cells generally larger medially than at the margins above midleaf (Pl. 10, f. 5) and bulging-hyaline at the leaf base (Pl. 10, f. 6), laminal papillae simple (Pl. 10, f. 8), perigonial leaves little different from the cauline, and exothecial cells thin-walled and bulging. Eucladium has several morphological features that are similar to those of Leptodontium and Hymenostylium: lack of a stem central strand, lanceolate leaves, trigonous upper laminal cells, inflated basal laminal cells, peristome similar to that of L. viticulosoides. The denticulate lower leaf margins are matched in Molendoa hornschuchiana. The narrowly lanceolate leaf shape, broad costa and large laminal cells ornamented with rather large, simple papillae are reminiscent of Tuerckheimia. The generic relationships are, on analysis, however, with Trichostomum.

Additional literature: Dalby (1966), Dixon (1912), Dunk and Dunk (1973), Glowacki (1909), Nagano (1959), Osada (1958), Saito (1972a).

Number of accepted species: 1.

Species examined: E. verticillatum.