Military orchid  (Orchis militaris)

Calcareous: containing free calcium carbonate, chalky.
Lip: in plants, petal or petals that form a lobe.
Perennial: plants that live for at least three seasons; after an initial period they produce flowers once a year.
Sepals: a floral leaf (collectively comprising the calyx of the flower) that forms the protective outer layer of a flower bud. (See http://www.rbgkew.org.uk/ksheets/pdfs/flower.pdf for a fact sheet on flower structure).
Tuber: in plants, a thickened stem or root that acts as an underground storage organ. Roots and shoots grow from growth buds, called 'eyes', on the surface of the tuber.

1. Marren, P. (1999) Britain's rare flowers. Poyser Natural History, London.
   
2. Grey-Wilson, C. (1994) Eyewitness Handbooks: Wild Flowers of Britain and Northwest Europe. Dorling Kindersley, London
   
3. Mabey, R. (1996) Flora Britannica. Sinclair-Stevenson, London.
   
4. JNCC (March 2002):
   www.jncc.gov.uk/habitats/jncc270/e2_6_5_1.htm
   
5. IUCN Red List 2000 (March 2002):
   http://www.redlist.org
   
6. Wigginton, M.J. (1999) British Red Data Books 1; Vascular Plants. 3rd Edition. JNCC, Peterborough.