Spruce's bristle-moss  (Orthotrichum sprucei)

Spruce's bristle-moss grows in neat, rounded cushion-like patches (4). When dry, the narrow leaves are straight, but they spread out when moist (4). The small tufts are often encrusted with debris that has been washed up by floods (2), and the lower parts of the plants are frequently embedded in silt (5).

This moss has a wide, but fairly sparse distribution in Wales and most of England, except for East Anglia. There is one historic record from Scotland (3). It has been lost from many historic sites in central and southern England. Elsewhere this moss is only known in western Europe, with a handful of records from Ireland, France, the Netherlands and Belgium (3).

Spruce's bristle-moss is an epiphyte, growing on the bark of trees in the flood zone of streams and rivers. Typical host trees include alder, willow and ash; it also grows on wooden fence posts (5). It occurs at heights that are inundated by peak flood levels, but are dry for most of the year (3).

Little is known of the biology of this species. Mosses, hornworts and liverworts form a group of plants called bryophytes (6). Bryophytes lack many of the more complex structures of the higher plants, such as a vascular system, and flowers. They do not have roots, instead they have structures called 'rhizoids' which absorb water and anchor the plant to the substrate. All bryophytes have an interesting life cycle consisting of two main parts, called the gametophyte and sporophyte generations (7). Plants that are in the gametophyte stage can reproduce sexually. Male organs (antheridia) produce male sex cells or gametes called antherozoids, which actually move to the female sex organs (archegonia) (7) through water droplets (8). Fertilisation occurs and a plant develops called a 'sporophyte', which remains attached to the plant. The sporophyte releases spores from within a capsule; the spores disperse and develop into a new gametophyte stage plant (7).

Potential threats are the removal of trees and the alteration of the patterns of discharge of rivers and streams. The latter threat may result from flood prevention works, for example, so that trees do not become inundated with flood waters (3).

A Species Action Plan has been produced for this moss under the UK Biodiversity Action Plan (UK BAP). This plan aims to maintain the current populations. Several populations occur within Sites of Special Scientific Interest (SSSI), and therefore receive a degree of protection (3).

Information authenticated by Royal Botanic Gardens, Kew:
http://www.rbgkew.org.uk/