Biological Flora of the British Isles: Paris quadrifolia L.

1. This account reviews information on all aspects of the biology of Paris quadrifolia L. (herb Paris) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history and conservation. 2. Paris quadrifolia is a perennial woodland herb that is found across the boreal and temperate areas of Europe. In the UK, it is a native species of moist, mostly ancient woodlands on calcareous soils. It can occasionally be found in grikes on open limestone pavement. It is absent from both very dry and very wet sites. It flowers and fruits most freely in the open stages of the coppice cycle, but persists in deep shade. 3. Paris quadrifolia is a rhizomatous geophyte. Regeneration is both by vegetative spread and sexual reproduction, and heavily weighted towards the former strategy. Paris quadrifolia has a monopodial growth form, with the increments of several years of growth remaining connected along the rhizome. Branching of the rhizome is sometimes observed. Amylose (a component of starch and a major storage carbohydrate) concentrations are low in young rhizome segments, but significantly higher in older segments. Severing rhizome connections by removing the oldest segments results in reduced growth and significantly smaller distal shoots, indicating that the size of the clonal fragment determines vigour of the terminal shoot and that integration serves to maintain the vitality of the rhizome, particularly in resource-poor environments. 4. Flowers are pollinated by wind, or self-pollinated. Insect pollination is very rare. Seed dispersal is limited and rates of spread vary between 0.21 and 0.33 m year-1. 5. As in most other European countries, Paris quadrifolia has declined in the UK. Many sites were lost in northern England and central Scotland before 1930, and since then there has been some decline in south-east England because of the destruction of broad-leaved woodland and planting of conifers. Since the species colonizes new forest stands very slowly, management should focus mainly on conservation of ancient forest stands.