Liverwort  (Cephaloziella massalongi)

Classified as Vulnerable in Great Britain (3).

This liverwort has a leafy appearance with yellowish-green, dark red-brown or black shoots that either lie along the ground or are raised upwards (3). The shoots support leaves that have toothed edges (3). Although this species is minute, it can often develop into fairly sizable patches (3). It is very similar in appearance to the related species Cephaloziella nicholsonii, and only detailed examination can distinguish the two (3). Cephaloziella nicholsonii is often larger, up to 15 mm long, is more fertile and produces asymmetrical gemmae, whereas Cephaloziella massalongi produces symmetrical gemmae (2).

In Great Britain this liverwort is known only from the south-west of England and north Wales, and is locally abundant at a number of sites in Cornwall and Devon (3). Elsewhere it has a wide distribution, occurring in north-western Europe, where it is classified as rare, and in the southern Appalachian Mountains in the USA (3).

Typically grows around copper mines or other copper-enriched habitats in damp acidic soil, on walls, rocks, and mine-spoil (3).

Liverworts, hornworts and mosses 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. In liverworts these rhizoids each consist of a single elongated cell (4). Bryophytes have an interesting life cycle, which consists of two main stages, called the gametophyte and sporophyte generations, the gametophyte generation is dominant. In the UK, Cephaloziella massalongi reproduces by producing special groups of cells called 'gemmae' (3) which develop into new plants (4). This species often occurs with C. nicholsonii, but it appears to be less resistant to dry conditions than the latter (3).

This liverwort has been lost from a number of sites in Anglesey and Gwynedd in Wales (3), it is thought that over-tidying of derelict land and land reclamation schemes may pose threats to the species (3).

Most of the sites that support this species are unprotected; just two occur within designated Sites of Special Scientific Interest, one in Cornwall, and the other in Wales (3). Site protection has been proposed for the strongest populations (3).

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

• 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.
• Gemmae: in bryophytes, a structure involved in vegetative reproduction, a type of asexual reproduction, reproduction without recombination of genetic material, that results in the propagation of plants using only the vegetative tissues such as leaves or stems. The resulting plant is genetically identical to the original plant. A well-known example of this is the reproduction of strawberry plants from ‘runners’. In vascular plants, gemmae are modified organs of the parent plant that can allow vegetative reproduction.
• 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.
• 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. National Biodiversity Network Species Dictionary (May 2002) http://www.nhm.ac.uk/nbn/
2. Paton, J. A. (1999) The liverwort flora of British Isles. Harley Books, Colchester.
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/