Racomitrium lanuginosum (Hedw.) Brid.

Nomenclature and Growth Form

Racomitrium lanuginosum (Hedw.) Brid. grows in large cushiony mats.

Stem Morphology

Its stems reach up to 12 centimetres (4.7 in) in length and are irregularly branched.

General Leaf Characteristics

Its leaves measure 3–5 millimetres (0.12–0.20 in) long and 0.6–0.9 mm (0.02–0.04 in) wide, are lanceolate-shaped and pointed, and have a prominent midrib.

Leaf Hair-Point Structure

Each leaf ends in a long, thin hair-point, with teeth along both sides of the hair-point that angle 40°–90° away from the leaf axis.

Leaf Hair-Point Margins

The transparent hyaline margins of the hair-point run downward along the sides of the leaf.

Species Appearance Etymology

Especially when the plant is dry, these hair-points give it a downy appearance, a feature referenced in many of the species' common names.

Sporophyte Occurrence

Sporophytes are rarely produced overall, though they are reported to be abundant in coastal areas.

Sporophyte Morphology

The capsules are 1.0–1.7 mm (0.04–0.07 in) long, smooth, and brown, and contain spores that measure 8–12 μm long.

Diagnostic Trait

The shape of the leaf hair-points of R. lanuginosum is unique among mosses.

Elevation and General Habitat

In terms of distribution and ecology, Racomitrium lanuginosum grows from sea level up to the alpine zone, most often among boulder scree and on exposed rock surfaces.

Substrate Preferences

It can also grow in tundra or bogs, and is found more often on acidic rocks than calcareous rocks.

Global Distribution Overview

It has a circumpolar distribution across the Northern Hemisphere, and also occurs as isolated disjunct populations in the mountains of the tropics and the Southern Hemisphere.

North American Distribution

Within North America, R. lanuginosum is widespread across northern Canada, and extends further south to Maine in the east, and to California and the Rocky Mountains in the west.

Tropical and Southern African Distribution

It is also found in Costa Rica, as well as in mountainous regions of South America and South Africa.

Atlantic and Indian Ocean Island Distribution

In the Atlantic Ocean, isolated populations occur on Iceland, the Azores, the Canary Islands, Madeira, Tristan da Cunha and South Georgia; it also grows on Réunion in the Indian Ocean, in New Zealand, Hawaii, and the sub-Antarctic islands Deception Island, Kerguelen, Îles Crozet, Heard Island and the Prince Edward Islands.

Asian and Southeast Asian Distribution

In addition to its wide range across Arctic Asia, R. lanuginosum is found in some temperate and tropical mountains on Borneo, Java, Sumatra and New Guinea.

Australian Distribution

In Australia, R. lanuginosum is restricted to Tasmania and the highest elevations of the Great Dividing Range on the border of New South Wales and Victoria.