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Published In: Bryologia Europaea 4: 70. 330 (Fasc. 23–24. Monogr. 4). 1844. (Bryol. Eur.) Name publication detail

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The leaves of O. gracile are delicate and extremely narrow. With some experience these narrow leaves can be used to distinguished it at a glance from O. pellucens which has firmer, stouter leaves that are more strongly twisted when dry. The presence of smooth to faintly wrinkled capsules in O. gracile is another good field difference between the two species. In O. pellucens the capsules are sulcate. Under the microscope the paroicous sexual condition and absence of costal stereids as well as the lack of a stem central strand separate O. gracile from O. pellucens.

There is considerable variation in the length of the endostome in O. gracile and this variation may have a geographical component. In Central American and Mexican (Crum 1994c) material the endostomes are _ or less the exostome length. In California and Oregon they are about ¾ the exostome length (Lawton 1971), while in Africa (De Sloover 1979) they are as long as the exostome teeth. Meijer (1951) gives the length of the segments as compared to the exostome teeth as “equal, somewhat shorter, or longer in length.”

Wijk et al. (1959, 1964) treated the basionym (Bryum gracile) of Orthodontium gracile as a nomenclatural synonym of O. lineare Schwaegr. because Wilson (1838) included that older name as a synonym in his original treatment. But, Wilson cited the name O. lineare with a question mark thus making Bryum gracile legitimate (Art. 52.2, Note 1, Greuter et al. 2000). Although Bruch and Schimper (1844) incorrectly cited the place of valid publication of the basionym (B. gracile) when making the combination O. gracile, this represents a bibliographic error and does not invalidate the new combination (Art. 33.4, Greuter et al. 2000).

Illustrations: Bruch and Schimper (1844, Pl. 330);  Meijer (1951, Pls. 3 & 4); Lawton (1971, Pl. 97 8–14); De Sloover (1979, Figs. 55–77); Sharp et al. (1994, Fig. 394). Figure 159 A–E.
Habitat: On decaying logs, trunks (Cupressus) and roots (Buddleia); 2500–3353 m.
Distribution in Central America: GUATEMALA. Huehuetenango: Sharp 4789 (F); Quezaltenango: Sharp 2135 (MO); Totonicapán: Sharp 2618 (MO). COSTA RICA. Cartago: Valerio 302 (FH); San José: Holz CR00-618 (GOET).
World Range: Northwestern and Southwestern U.S.A.; Mexico; Central America; Western and Southern South America; Northern and Southwestern Europe; Northeast and West-Central Tropical Africa.


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Orthodontium gracile (Wils.) Schwaegr. ex B. S. G., Bryol. Eur. 4: 70. 1844.  

Bryum gracile Wils. in Sm. & Sowerby, Suppl. Engl. Bot. 3: 2035. 1839. Protologue: Great Britain. On the sandstone rocks at Helsby and Frodsham, in Cheshire, being the northern termination of Delamere Forest, abundant, March 25th, 1833. 

Plants small, yellowish green in tufts to 5 mm high; rhizoids moderately developed at base. Stem central strand absent. Leaves 3–4 mm long, erect to erect-flexuose, sometimes twisted when dry, linear-setaceous; apices narrowly acuminate; margins plane or weakly recurved below, not bordered, entire or weakly serrulate above; costa percurrent, stereid cells absent; upper cells linear‑fusiform, firm‑walled, 80–140 x 6–8 μm, basal cells reddish, enlarged, quadrate to oblong, thin-walled and bulging, alar cells not differentiated. Paroicous. Setae 4–10 mm long, yellowish. Capsules 1.5–2.5 mm long, oblong, oblong-cylindrical to sub-cylindrical, erect, smooth to lightly wrinkled when dry, constricted at neck, bordered at mouth by 3–4 rows of oblate cells; opercula conic-rostrate; peristome inserted within mouth, exostome yellow, smooth, endostome _ the length of the exostome teeth, yellow, smooth, basal membrane very low (1–2 rows of cells), segments stout, not perforate or keeled, cilia absent. Spores 12–16 μm, papillose. Calyptra not seen.



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