Tuesday, May 4, 2010

Tears, Toothache and a Defunct Doctrine...


Inspired by a post on Rob's fascinating Wight Rambles blog, we went to look for toothwort - a weird, leafless, parasitic flowering plant devoid of chlorophyll that satisfies all its water and nutritional requirements by tapping into the roots of hazel: a vegetable vampire. We found it growing along the banks of the river Wear near Wolsingham, newly emerged from the soil.


I remembered reading the following in Charles Darwin's The Power of Movement in Plants, published in 1880:

'The passage of the flower-stem of the Lathraea through the ground cannot fail to be greatly facilitated by the extraordinary quantity of water secreted at this period of the year by the subterranean scale-like leaves; not that there is any reason to suppose that the secretion is a special adaptation for this purpose: it probably follows from the great quantity of sap absorbed in the early spring by the parasitic roots. After a long period without any rain, the earth had become light-coloured and very dry, but it was dark-coloured and damp, even in parts quite wet, for a distance of at least six inches all round each flower-stem. The water is secreted by glands which line the longitudinal channels running through each scale-like leaf.'

Sure enough the soil immediately around our newly-emerged flowering shoots was soaking wet, even though it was dry all around, just as Darwin had described 130 years ago. It may be that the plant has to secrete water in this way to maintain a flow of nutrient-laden liquid through its stems. Normal plants with leaves use the evaporation of water from the leaf surface to 'pull' the flow of water through - toothwort has to secrete 'tears' to achieve the same ends...


Folklore has it that toothwort acquired its common name as a result of the ancient Doctrine of Signatures, whereby plants that looked like parts of the human body were considered to have been designed in that way as an sign from the almighty that they could be used for healing the afflicted part of the anatomy. Toothwort flowers do look like rows of discoloured teeth. The plant only appears above ground for a couple of months in spring; I guess that there must have been a time when entrepreneurial apothecaries would have laid in supplies now, for treating toothache when the fresh plant wasn't available ....

8 comments:

  1. The hazel has a tough time, having the sap sucked out of it below ground, coppiced to within inches of the woodland floor, and still it bounces back!
    I didn't know that about the secretion or the supposed remedy - thanks.

    ReplyDelete
  2. What a fascinating plant and a most intriguing business that - the wet ground. I must look out for it. Just an incidental by-product of its way of life or a functional part of the whole process? Who knows, but you have to keep taking your hat off to Charles Darwin!

    ReplyDelete
  3. This is a fascinating plant, Phil. Thank you for the i.d. on my fern.

    ReplyDelete
  4. Hi Rob,trees don't come much more resilient than that!

    ReplyDelete
  5. Hi Nyctalus, amazing what an acute observer of nature Darwin was , in so many areas ........... unlike the extreme specialists in science today ....... I suspect that there would be no place for somene like him in 21st. century science

    ReplyDelete
  6. The bumblebees seem to like it too Emma. The seeds ripen in early summer and I'm planning to collect some, to see if I can persuade it to establish itself on the roots of a hazel in my garden..

    ReplyDelete
  7. That's a depressing thought in many ways Phil -the devaluing of detailed observation. I suppose what you mean is that it's been relegated to an amateur thing now and no longer considered 'proper' science? But there must still be pockets left somewhere? The fantastic observational work behind the unravelling of the complex lifecycle of the Large Blue and the ants it relies on and which led ultimately to successful reintroduction projects, is very Darwinesque, I think. I'm sure that was a University research PhD project, so maybe all is not yet lost.

    ReplyDelete
  8. Yes Nyctalus, I think amateur naturalists are more important now than they ever were, now that their skills don't fit the modern model of biological sciences in academia. There are still plenty of detailed, specific studies of the kind you mention in universities, but the day of the Darwinian generalist is done - for now at least..

    ReplyDelete