Pilularia globulifera

Status UK Biodiversity Action Plan Priority species. Nationally Scarce. IUCN Threat category: near threatened (2005).

Taxonomy Pteropsida: Marsileaceae Scientific name: Pilularia globulifera L. Common names: Pills Pillwort, Pelenllys

A small rhizomatous fern, Pilularia globulifera is the only member of the family in Britain.

Biology & Distribution It grows on silty mud by edges of lakes, ponds, reservoirs or slow-flowing rivers and sometimes in open, damp mineral workings. It can be submerged for part of the year, or can grow as a submerged aquatic, and occasionally occurs as a free-floating aquatic. It requires areas where competition is reduced by fluctuating water levels or disturbance.

Scattered throughout most of British Isles but much less common than formerly (Preston et al. 2002). It is now frequent only in parts of Ireland, central southern England and parts of Wales (Anglesey, Pembrokeshire, Powys and the mawn pools of Radnorshire).

It was lost from many sites before 1930 due to habitat destruction. Eutrophication and reduced disturbance Young shoots have led to further losses. In the west, many new sites curled have been found since 1980. It has been re-introduced Figure 1. Pilularia globulifera (from J. E. Smith & J. Sowerby to some former native sites (e.g. Rhum, Scotland). (1852). English Botany. London). Identification & Field survey Pilularia is instantly distinguished from all other ferns In the field, Pilularia is often a bright yellowish-green and plants by the young leaves and shoot apices which allows it to be picked out from other aquatics being curled at their apex like a shepherd’s crook, (Eleogiton fluitans is of similar colour but lacks the not straight. The leaves are solid, lacking two hollow curled leaf tips). tubes (look at middle of leaf end-on with a x20 lens). Key characters Another diagnostic feature is the presence of the ‘pills’ Rhizomes long and pubescent with leaves borne (small round reproductive bodies c. 5 mm across singly but often close together. Leaves erect, 3-8 cm which are actually fertile leaves and which give it its x c. 0.5 mm, but spirally coiled when young. ‘Pills’ name), under the shoots in the substrate, though this round, c. 3 mm, on stalks c. 1 mm. requires excavation which may not be desirable. References Stewart, A., Pearman, D. A. & Preston, C. D. eds. (1994). Scarce Plants in Britain. JNCC, Hutchinson, G. & Thomas, B. A. (1996). Welsh Ferns. Peterborough. 7th edn. National Museums and Galleries of Wales, Cardiff. A briefing sheet is available on the Plantlife website Page, C. N. (1997). The Ferns of Britain and Ireland. 2nd (www. Plantlife.org.uk) edn. Cambridge University Press, Cambridge. Preston, C. D., Pearman, D. A. & Dines, T. D. eds. Additional photographs are available on the ARKive (2002). New Atlas of the British & Irish flora. Oxford website (http://www.arkive.org/species). University Press, Oxford.