pierre laszlo

Hypericum calycinum (Hypericaceae)

There are about nearly 500 Hypericum species, distributed across every continent except Antarctica. Although the Mediterranean basin is a hot spot for Hypericum, Asian and American continents also account for significant biodiversity, out of which many species are endemic. 
Due to the therapeutic efficacy of its different species, as antimicrobials in particular, Hypericum is well known in herbal medicine. It has even been used against mild and moderate depression and proven to be superior to placebo in improving depression symptoms, comparable to standard antidepressant drugs. 
This is the plant whose shoots are gathered and burned to ward off evil spirits on the eve of St. John's Day, thus giving rise to the common name for the genus, as St. John's wort — the latter an Old English word meaning ‟herb, plant.‟ Another traditional ritual consists in hanging flowers of this genus above images, pictures or windows. 
The five-petaled, yellow flowers (5-8 cm in diameter) are spectacular — a sun in miniature. They display numerous, bushy stamens with reddish anthers— with the appearance of miniscule poppies. The net-veined leaves have a distinctive response to sunshine, rich green in full light but a pale, yellowish green in the shade. 
Flowers, with their petals to us uniformly yellow, actually bear a UV pattern, which insects can see. Two pigments types, flavonoids and dearomatized isoprenylated phloroglucinols (DIPs), make up that pattern. Flavonoids are frequent floral UV pigments, but not the DIPs. The latter are present in high concentration in the anthers and ovarian wall of the flower, with a defensive purpose: deterrence and toxicity to insects. saint John’s wort was thus the first plant to have been reported having floral UV pigments fulfilling both an attractive visual (pollination) and a defensive (toxicity to herbivores) function.