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Friday, July 23, 2010

Digitalis purpurea Foxglove

The use of foxglove Digitalis purpurea in herbal medicine was described long ago by Greek and Roman herbalists but the scientific investigation of its medicinal properties really began with the investigations carried out by the English botanist and physician William Withering (1741-1799).

William Withering was an outstanding botanist and in 1776 published his Botanical Arrangement of All the Vegetables Naturally Growing in Great Britain, a descriptive flora based on Linnaeus's new-fangled system of classifying plants according to the number and disposition of their sexual organs and reducing their Latin names to simple binomials - like Digitalis purpurea. Double-click on the image above and you'll see from the title page that this was an encyclopaedic botanical treatise, covering everything from preparing pressed herbarium specimens to the use of wild plants in herbal medicine, and it's in this book that he first mentions his interest in foxglove: "A dram of it taken inwardly excites violent vomiting." he wrote, " It is certainly a very active medicine, and merits more attention than modern practice bestows upon it."
The story is that the plant caught his attention when a 'wise woman' herbalist introduced him to an infusion of about 20 herbs that she used to treat dropsy (fluid retention caused by congestive heart failure). Withering surmised that the active ingredient was foxglove, that strenthened heart beat and acted as a diuretic, and in 1785 published An Account of the Foxglove and some of its Medical Uses, describing case studies - effectively clinical trials - of  patients who he had treated with foxglove.  The following is a typical example:


January 1st. Mr. H——. Hydrops Pectoris; legs and thighs prodigiously anasarcous; a very distressing sense of fulness and tightness across his stomach; urine in small quantity; pulse intermitting; breath very short.[26]
He had taken various medicines, and been blistered, but without relief. His complaints continuing to increase, I directed an infusion of Digitalis, which made him very sick; acted powerfully as a diuretic, and removed all his symptoms.

Stately spires of foxglove flowers, usually growing best on acid soils, are a major attraction for bumblebees in June and early July.

When the bee forces its way in to reach the nectar at the base of the corolla tube its back is dusted with pollen from the yellow stamens positioned overhead. The stigma matures later, in the same position, collecting pollen from bees as they arrive from other foxglove plants.

There's no doubt that the positioning of the stigma and stamens and the bell-shape of each flower is an adaptation to cross pollination by bumblebees but the shape of the tubular petal has another role - keeping raindrops from the pollen on wet summer days.

Friday, July 16, 2010

Henbane Hyoscyamus niger

Henbane Hyoscyamus niger is a poisonous member of the potato family and has a long history of use by murderers. Its gruesome history, sombre colours and veined petals give it an aura of menace. It's reputed (controversially) to be the poison used by Hamlet's uncle to poison the prince's father, by pouring it in his ear, in Shakespeare's tragedy Hamlet.

Sleeping within mine orchard,
My custom always in the afternoon,
Upon my secure hour thy uncle stole,
With juice of cursed hebona [henbane] in a vial,
And in the porches of mine ears did pour
The leperous distilment; whose effect
Holds such as enmity with blood of man
That swift as quicksilver it courses through
The natural gates and alleys of the body,
And with a sudden vigour it doth posset
And curd, like eager droppings into milk,
The thin and wholesome blood: so dit it mine:
And a most instant tetter bark’d about,
Most lazar-like, with vile and loathsome crust,
All my smooth body.

More recently Hawley Harvey Crippen is reputed to have used it to kill his wife Cora in a notorious case in 1910, when the new-fangled wireless telegraph was used to aid the interception of the fugitive as he fled to Canada.

Like so many plant poisons, the toxic alkaloids found in henbane have medicinal applications and were once used as a hazardous anaesthetic by dentists. The herbalist John Gerard left a graphic account of their use in his herbal of 1597.

“Henbane", he wrote, " causeth drowsinesse, and mitigateth all kinde of paine… ………the leaves, seed, and juice taken inwardly cause an unquiet sleep like unto the sleep of drunkennesse, which continueth long, and is deadly to the party.
The seed is used by Mountibank tooth-drawers which run about the country, to cause worms to come forth of the teeth, by burning it in a chafing dish of coles, the party holding his mouth over the fume thereof: but some crafty companions to gain money convey small lute-strings into the water, persuading the patient, that those small creepers came out of his mouth or other parts which he intended to ease.”

In 2008 celebrity chef Anthony Worrall Thompson confused the poisonous henbane for the edible weed fat hen and published a recipe for its use in salads – a lurid example of the dangers of only knowing common colloquial names for plants rather than identifying them by their scientific names. No one is known to have suffered illness from the chef’s error, perhaps because henbane is not a common wild plant, and the chef didn’t seem to be too perturbed by his mistake. "I was thinking of a wild plant with a similar name, not this herb. It's a bit embarrassing, but there have been no reports of any casualties. Please do pass on my apologies", was his comment.

Franz Eugen Köhler, Köhler's Medizinal-Pflanzen 1897

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Sunday, July 11, 2010

Inula hookeri

This shaggy member of the daisy family, with its beautifully geometric spiral pattern of unopened central florets, originates from the Himalayas. In my garden it's a great attraction to bees, that appreciate the long period of pollen production that results from the sequential opening of all those florets.

I've been teaching botany since 1975 and over the last decade it seems to me that students have become increasingly frightened of Latin names. Maybe it's the purported British reluctance to learn languages, maybe it's because these days they see fewer plants in the field, which is the best place to associate a plant with its scientific name. Whatever the reason, it's a pity because Latin names often tell you so much about an organism and the people or places that are associated with it.

This plant's specific name commemorates Sir Joseph Hooker, who found it in the Himalayas and introduced it to British gardens in 1849. Joseph Dalton Hooker, one of the most eminent botanists and explorers of his day, laid the foundations for botanical biogeography and became Charles Darwin's closest friend and confidante, as well as serving as Director of the Royal Botanical Gardens, Kew for two decades.

Joseph Dalton Hooker

Sir Joseph Dalton Hooker has his own posthumous web site, created by Jim Endersby at the University of Sussex, for all those who appreciate the scientific achievements of one of the greatest of all botanists.

The generic name of this plant, Inula, has given its name to the carbohydrate inulin, which it stores in its roots instead of starch. Inulin - which is also present in Dahlia and Jerusalen artichoke tubers - has little effect on blood sugar levels and so is often used as a sweetener in foods for diabetics. Unfortunately - as anyone who has ever eaten significant quantities of Jerusalem artichoke will testify - it can generate acute attacks of flatulence for anyone who doesn't gradually add it to their diet.

Students often complain that Latin names are hard to remember. They're not when you decode them, when every name tells a story. Just remember to associate this flower with flatulence and Darwin's best mate and you'll never forget it...