Francoise Barbira-Freedman, a medical anthropologist at Cambridge University, described how she discovered the remedy, which is derived from the rare Acmella oleracea plant, while visiting the tribe in the rainforest.

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The rare leaf is a part of the tobacco plant called the medio tiempo, taken from the upper leaves of the plant, but which not every plant produces, making it rare.

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He said it was "very rare" that a plant-eater would sport sharp-edged, enlarged canines.

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The BBC's Rupert Wingfield-Hayes in Tokyo says Japanese media have cited anonymous sources as saying that Mr Aratani had been on a rare visit to the plant to meet senior executives from partner companies.

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SEARCH, a non-profit body in Tucson, collects wild plant varieties, including rare or unknown chiles.

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Scientists will eventually find widespread evidence of simple, microbial life, they theorized, but complex animal or plant life will prove extremely rare.

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The NRW said that where it had colonised, it was out-competing the native plant species such as grey willow and rare copper moss.

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The plant is finally operating, but prices for some rare-earth elements are now 80% off their peaks.

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Hardly anything can grow there due to the impossibly cold climate and any plant life that manages to sprout up out of the ground is rare and quite determined.

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Pollen from 64 types of plant at the site where the bodies were found - some of them quite rare - was also matched to grains in the car and on Huntley's shoes.

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