Tropicos | Name - Leptodontium excelsum (Sull.) E. Britton

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Leptodontium excelsum (Sull.) E. Britton

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Project Name Data (Last Modified On 2/16/2011)

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Project data (Last Modified On 2/16/2011)

Discussion:

Leptodontium excelsum is a small species with leaves only 2–3 mm long. It often has flagellate branches with well-spaced, non-contorted, and recurved leaves. Some collections consist predominantly of such branches. The leaves of L. excelsum are spirally twisted when dry, the upper leaf cells are thick-walled but only rarely collenchymatous, the sheathing base is high and broad with smooth cells near the leaf insertion that are sometimes enlarged and straight-walled to weakly porose. The most distinctive feature of L. excelsum is the presence of 1-several enlarged, hyaline nematogen cells in its leaf apices. These nematogen cells often give rise to rhizoids.

Zander (1972, 1994a) treated L. excelsum as a synonym of L. ulocalx, however Crum and Anderson (1981) considered them distinct. Leptodontium ulocalyx is an extremely variable plant that grades into L. excelsum in plant size and aspect. In general, however, it is a larger, more robust plant with leaves 2.5–8 mm long, and only rarely does it have flagellate branches. The leaves of L. ulocalyx are crispate when dry, its upper leaf cells are strongly collenchymatous, the sheathing base is short and narrow and its cells are thick-walled, porose, and pluripapillose to near the leaf insertion. The best feature distinguishing the two taxa is the presence of apical leaf cell nematogens in L. excelsum, which are absent in L. ulocalyx.

Illustrations: Sullivant (1864, Pl. 32); Crum and Anderson (1981, Fig. 144). Figure 41.

Habitat: On shrubs, tree trunks and branches (Quercus, Cupressus), and non-calcareous boulders; 2700–4100 m.

Distribution in Central America: GUATEMALA. Chimaltenango: Standley 61870 (F); Huehuetenango: Steyermark 50208D (F); Quezaltenango: Steyermark 34851 (F, MICH); San Marcos: Sharp 5443 (F, MICH, NY, TENN); Totonicapán: Sharp 2594 (TENN). EL SALVADOR. Chalatenango: Sipman et al. 37637 (MO, NY). HONDURAS. Lempira: Allen 12257A (MO, TEFH). COSTA RICA. Cartago: Dauphin 2084 (CR, MO); San José: Crosby & Crosby 6091 (MO). PANAMA. Chiriquí: Allen 9158 (MO, PMA).

World Range: Southeastern U.S.A.; Mexico; Central America.

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Leptodontium excelsum (Sull.) Britt., Bryologist 11: 66. 1908.

Syrrhopodon excelsus Sull., Musci Allegh. 41. 1846. Zygodon excelsus (Sull.) Britt., Mem. Torrey Bot. Club 4: 180. 1893. Protologue: U.S.A. Hab. summo in cacumine montis Grandfather, Carolinae Septentrionalis, arboreus, Musci Alleghanienses No. 170 (MO).

Zygodon sullivantii C. Müll., Syn. Musc. Frond. 1: 679. 1849. Amphoridium sullivantii (C. Müll.) Lesq. & James. Protologue: U.S.A. In summo cacumine montis Grandfather Carolinae septentrionalis, arboreus, Sullivant (MO).

Plants small to medium-sized in loose tufts, yellow-green to light green, to 4 (-10) cm long. Stems red, erect or laxly ascending or pendent, sclerodermis present, moderately radiculose. Leaves well-spaced, erect at base, spirally twisted above when dry, squarrose to squarrose-recurved, smooth or undulate at margins when wet, ovate-lanceolate to long-lanceolate, 2–3 mm long, keeled above, sheathing at base, decurrent; apices acute; margins recurved in lower 1/2–2/3, dentate in upper 1/3, teeth usually pluripapillose; costa subpercurrent; upper leaf cells quadrate to hexagonal or shortly elongate, thick-walled, not or occasionally collenchymatous, 6–10 μm, pluripapillose, papillae low, scattered over the lumina, leaf apex with 1 to several enlarged, hyaline, smooth nematogen cells often giving rise to rhizoids, inner basal cells long-rectangular to elongate, smooth, thick- or thin-walled, straight-walled or porose, 32–100 x 3–8 μm, outer basal leaf cells quadrate, alar cells differentiated, short-rectangular to quadrate. Plants often with long, slender, flagellate branchlets along the stems, branchlet leaves spreading to recurved when wet, lanceolate, not deciduous, costa subpercurrent. Dioicous. Perichaetial leaves elongate, to 6 mm long, sheathing the seta and nearly overtopping the capsule. Setae straight, 1 per perichaetium, 5–10 mm long, yellow. Capsules erect to somewhat curved, cylindrical, 2.5–3.5 mm long, smooth; exothecial cells short-rectangular, firm-walled; stomata at base of urn; opercula conic-rostrate, 0.5–1 mm long; peristome teeth deeply inserted within the capsule mouth, short, linear, irregularly divided, red-brown below, hyaline above, striate, 300 μm long. Spores 17–25 μm, slightly papillose. Calyptrae cucullate, smooth, 5 mm long.