Slender Thread Moss

Mosses are plants, but they belong to the lower orders. They do not produce flowers or seeds, but reproduce by spores or vegetatively. Neither do mosses have a vascular system for conveying sap, nor do they have roots to absorb water. Mosses have rhizoids, which fulfil the role of a root system in anchoring the plant to a surface. Water and nutrients are absorbed over the entire surface of the plant.

Slender thread-moss is listed in the UK Biodiversity Action Plans (UKBAPs), and included in English Nature's Species Recovery Programme (SRP). This moss's existence may be precarious, and all the sites where it is known to occur are protected. It is also being grown ex-situ as an insurance against its loss in the wild, and trials are underway to re-introduce the species to suitable sites. As it may be threatened by an introduced species, it might be possible, under supervision, to clear competing mosses to allow slender thread-moss to re-colonise the sites. In the meantime, bryologists are being asked to pass on any records they have of this moss, to enable greater knowledge of its ecology and its true status to be gathered.

Slender thread-moss grows in bright green cushions, and closely resembles a much commoner species Orthodontium lineare. It requires an expert to tell them apart, but slender thread-moss has slightly narrower leaves. Mosses are difficult plants to identify, needing knowledge and a scientific field guide to be sure of which species you are looking at.

In the UK, slender thread-moss grows on damp, shaded, vertical, acid rock surfaces, and sometimes in crevices. In France, it is found on sandy soil at the base of trees, and occasionally, on rotting wood. It has very occasionally been recorded on rotting wood in England.

This moss has a wide world range, being found in western France, North and South America, and tropical Africa. In the UK since 1970, it has been recorded in East Sussex, Cheshire, mid-West Yorkshire and Midlothian.

Classified as Vulnerable in the UK. Classified as Endangered in Europe.

Never a common species, slender thread-moss may possibly have declined through the introduction of the similar O. lineare. Other factors may be due to changes in the microclimate or acidic water pollution.

Orthodontium gracile

Orthodontium gracile Schwaegr. ex B.S.G., Bryol. Eur. 4:70, 1844 (fasc. 23–24 Mon. 4). [Original material: Near Helsby, Cheshire, England, coll. Wilson, 1833 (BM).]

Orthodontium aethiopicum C. Müll., Bot. Zeit. 13:733, 1855. [Original material: Cossi berri, Abyssinia, coll. Schimper (lectotype; S).]

Orthodontium osculatianum DeNot., Mem. R. Acc. Sc. Torino ser. 2, 18:443, 1859. [Original material: Mt. Napo, Colombia, coll. Osculati (RO).]

Orthodontium tenellum Mitt., J. Linn. Soc., Bot. 12:275, 1869. [Original material: Picillum, Andes Quitenses, coll. Jameson (NY).]

Stems usually 2–4 mm high. Leaves pellucid, linear, to 7 mm long; margins subentire; costa without stereids; median cells linear, 8–12 μm broad, 40–80 μm long; basal cells rectangular, 75–125 μm long, to 25 μm wide. Paroicous. Setae 2.5–10.0 mm long. Capsule 1.5–2.0 mm long, narrowly ovate to narrowly pyriform, not plicate; peristome teeth narrowly lanceolate. Spores 10–18 μm in diameter.

MAS A TIERRA: El Yunque, near and below east face, ca. 1600–1800 ft, H. & E. 361, 374, 504A; trail to base of El Yunque up to 1800 ft, H. & E. 796.

The species is known also from Europe, Central Africa, western United States, Mexico, Guatemala, and the Andes from Colombia to Chile. Bartram was the first to report the species from Juan Fernandez.