This section is from the book "Wayside And Woodland Blossoms", by Edward Step. Also available from Amazon: Wayside And Woodland Blossoms: A Guide To British Wild-Flowers.
Fool's Parsley is fond of cultivated ground, and it is no unusual thing for it to make its appearance in the very garden beds that have been set apart for rearing that pot-herb for which fools are said to mistake it. It is an annual, with a spindle-shaped, fleshy root, round, hollow stem, branched, and marked with fine longitudinal lines. The leaves are smooth, compound, and bluish green in tint. The wedge-shaped leaflets are themselves pinnate, and the pinnae are lobed. The flowers are small and irregular, white, grouped in small umbels, which are again gathered into large umbels of umbels.
The reader is invited to turn back to page 55, where the structure of umbelliferous flowers and fruits is more intimately described. The small umbels in aethusa are provided with an involucre consisting of three or five little bracts, very narrow and hanging vertically. This feature will serve to distinguish aethusa from all other umbellifers. The entire plant is evil-smelling, and said to be poisonous. It flowers during July and August, and is the only species. It gets its generic name from the Greek aitho, to burn, from its acrid character, and its specific name is a combination of Kynos, dog, and apion, parsley, which is a further note of its worthless character.
Aethusa cynapium. - Umbelliferae. -