Lesser smoothcap (Atrichum angustatum)

Kingdom	Plantae
Phylum	Bryophyta
Class	Polytrichopsida
Order	Polytrichales
Family	Polytrichaceae
Genus	Atrichum (1)
Size	Height: up to 3 cm (2)

Classified as Endangered in Great Britain (3).

Lesser smoothcap is a dull-green moss that forms patches of single, unbranched and upright shoots that have narrow leaves with toothed edges (3). The leaves curl up when the moss becomes dry (3). Mosses are broadly divided into two main types, called 'acrocarpous' and 'pleurocarpous' mosses. This species is an 'acrocarpous' moss (3); these mosses tend to have erect shoots that have limited growth, and terminate in male and/or female sexual structures. Side branches allow further growth to occur (4). Close examination allows this species to be distinguished from the other members of the genus Atrichum, as it has smaller spores and cells (3)

Most UK records of this species are concentrated in the High Weald in Sussex and Kent (5), but it has not been seen at a third historic site in this area since 1950 (3). A few scattered records are known from southern Scotland and south Wales (5). Outside of the UK this moss has a broad distribution across Europe, reaching as far east as western Asia. It has also been recorded from Iceland, Madeira, the Azores (5), Turkey, Japan and eastern and central parts of North America (3).

Found in woodland rides and paths growing on bare, fairly acidic, damp, shaded, loamy or sandy soil. It has also been recorded from roadside banks, abandoned sandpits and open grassland heaths (3).

Mosses, hornworts and liverworts form a group of plants called bryophytes (3). 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 (4). Plants that are in the gametophyte stage can reproduce sexually. Male organs (antheridia) produce antherozoids which move to the female organs (archgonia). Fertilisation occurs and a 'sporophyte' develops, this structure remains attached to the plant. The sporophyte releases spores which disperse and develop into a new plant (4). In the lesser smoothcap, sporophytes are produced very rarely in winter (3).

The threats facing this species are poorly understood, but it is thought that decline in coppicing in woodlands as well as the neglect of woodland rides and paths may be factors (5).

A UK Biodiversity Action Plan Priority Species, the lesser smoothcap has a Species Action Plan which outlines and coordinates proposed conservation measures (5). This plan aims to maintain the strong populations of this species (5). A survey of the sites is needed to assess the status of this endangered moss (3).

Information authenticated by Royal Botanic Gardens, Kew:

http://www.rbgkew.org.uk/

• Acrocarpous: type of moss, which tend to grow in erect tufts, that display very little or no branching, and have the female sex organs (archegonia) situated at the tips of stems or branches.
• Coppicing: traditional form of woodland management in which trees are cut close to the base of the trunk. Re-growth occurs in the form of many thin poles. Woodlands are cut in this way on rotation, producing a mosaic of different stages of re-growth.
• Gametophyte: a life cycle stage in plants, which has one set of chromosomes (threads of DNA protein) in the cell nucleus (a condition known as ‘haploid’), which arises from a spore (which is also haploid). Sex cells (gametes) are produced during the gametophyte stage. This is the dominant life-cycle stage in liverworts and mosses.
• Pleurocarpous: mosses are broadly divided into two main types, called ‘acrocarpous’ and ‘pleurocarpous’ mosses. Pleurocarpous mosses tend to develop as spreading carpets rather than as upright tufts, in which the female sex organs (archegonia) are not situated at the tips of stems or branches, but are produced on short lateral branches.
• Rhizoids: thread-like structures that help to anchor the plant to the substrate, and absorb minerals and water. In liverworts they consist of a single cell, in mosses they are multi-cellular.
• Rides: often the footpaths and access tracks which run through and divide blocks of trees in woodland. Many rides contain a mixture of rich flora and structure, and provide different habitat conditions for a range of wildlife.
• Spores: microscopic particles involved in both dispersal and reproduction. They comprise a single or group of unspecialised cells and do not contain an embryo, as do seeds.
• Sporophyte: the stage of a plant life cycle that produces spores (microscopic particles used in dispersal and reproduction). This stage is diploid (in the cell nucleus there are two sets of chromosomes - threads of DNA protein) and is dominant in ‘higher’ plants such as flowering plants.
• Vascular system: in plants, the system that allows water and nutrients to move around.

1. ITIS, the Integrated Taxonomic Information System (September, 2009)
   http://www.itis.gov
2. Smith, A.J.E. (1996) The moss flora of Britain and Ireland. Cambridge University Press, Cambridge.
3. Church, J.M., Hodgetts, N.G., Preston, C.D. and Stewart, N.F. (2001) British Red Data Books: mosses and liverworts. Joint Nature Conservation Committee, Peterborough.
4. Mosses and Liverworts in Wales (May, 2002)
   http://home.clara.net/adhale/bryos
5. UK BAP (May, 2002)
   http://www.ukbap.org.uk