Silphium (also known as silphion or laser) was a plant that was used in classical antiquity as a rich seasoning and as a medicine. Silphium was an important species in prehistory, as evidenced by the Egyptians and Knossos Minoans developing a specific glyph to represent the silphium plant. It was used widely by most ancient Mediterranean cultures; the Romans considered it "worth its weight in denarii" (silver coins). Legend said that it was a gift from the god Apollo. The exact identity of silphium is unclear. It is commonly believed to be a now-extinct plant of the genus Ferula, perhaps a variety of "giant fennel". The still-extant plant Ferula tingitana has been suggested as another possibility. - Halil

I've read the odd blog about this, and as you know you have to be weary of blogs because anyone can say anything, and most don't post source links to back-up their story, but it seems that over-harvesting may have been the purpose of this plants extinction, unless of course it's a case of mistaken ID and it still exists? - Halil