Friday, September 23, 2011

Tree Lungwort and the Doctrine of the Signatures

Tree Lungwort, Lobaria pulmonaria
Spleenwort, Liverwort, Toothwort: seemingly picaresque names for common plants, their origin is actually based in an ancient concept of medicine, the Doctrine of Signatures. The early botanist – and all-round occultist – Paracelsus von Hohenheim (1493-1541) was the first to expand on ideas from antiquity and early European Christianity as the Doctrine of Signatures (1). The central tenet of the doctrine was that the shape, colour and other attributes of a plant indicated its use in healing. So the liver-shaped thallii of the Liverwort genus Marchantia spp. are, according to the doctrine, useful for treating liver ailments*. The Doctrine of Signatures was based on the belief that God marked all his creations with a sign, or signature. The sign showed its purpose. Its rise in popularity during the 15th and 16th centuries is rooted in the role 'resemblance' played in Western culture at that time.
Tree Lungwort, Lobaria pulmonaria
While the Doctrine of Signatures has long been rejected by botanists and chemists on the basis of scientifically controlled data, it has left us with a plethora of colourful names. However, one of these is, in a way, well deserved. Tree Lungwort (Lobaria pulmonaria) is an impressively large lichen that has the green alga Dictyochloropsis reticulata as its photosynthetic partner (2). It is found attached to the bark of trees in old to ancient woodlands with high levels of rainfall (3). While the pitted appearance of the thallii resemble lung tissue, the name 'Lungwort' is appropriate in another sense. Found in moderate regions of the tropics and throughout boreal regions of the norther hemisphere, it thrives in places of low pollution and has dissappeared entirely in parts of Central Europe in the 20th century due to falling air quality (4). Pollutants in the atmosphere condensing to form acid rain fall on the forests. L. pulmonaria colonise drainage channels below old and large wounds on deciduous trees. These channels are richer in minerals and had a higher pH than normal bark (5), but concentrate pollutants in rain. Populations of the lichen are thus wiped out
Tree Lungwort, Lobaria pulmonaria showing fruiting bodies
While the effect of L. pulmonaria on the lungs has yet to be proven, it has been shown to have some  pharmacological properties (6). Liquid extracts from the lichen tested on rats showed moderate anti-inflamatory and strong antiulcerogenic affects.

*Note: The suffix 'wort' is derived from the old English word for plant.

References:
  1. Pearce, 2008. European Neurology 60 pp. 51-52
  2. Widmer et al., 2010. Fungal Biology 114 pp. 583-544
  3. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 282
  4. Walser et al., 2003. Fungal Genetics and Biology 40 pp. 72–82
  5. Gauslaa, 1995. The Lichenologist 27 pp. 59-76
  6. S├╝leyman et al., 2003. Phytomedicine 10 pp. 552-557

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