Oenanthe crocata
Oenanthe crocata, the hemlock water-dropwort, also known as dead man's fingers, is a flowering plant in the carrot family, Apiaceae, native to the British Isles, Western Europe and the Iberian Peninsula. All parts of the plant are extremely toxic and have been implicated in several cases of livestock poisoning. The toxic leaves and stems look like parsley; the highly toxic roots look and smell like parsnips. Description. Hemlock water-dropwort is a robust hairless perennial growing up to 150 cm tall with hollow, cylindrical, grooved stems up to 1 cm across. The stems are often branched . The upper part of the roots are five or more obovoid, pale yellow, fleshy tubers up to 6 cm long, which exude yellowish fluid when cut that stains the skin. The lower leaves are 3–4 times pinnate, triangular, with oval toothed leaflets 10–20 mm long, that are basally tapered to the stalk (cuneate). The upper leaves are 1–2 pinnate, with narrower lobes and a shorter petiole (leaf stalk). All the leaves are spirally arranged and have petioles that are slightly sheathing around the stem. The leaves have a characteristically deceptive smell of parsley or celery. Like other species in the  genus, hemlock water-dropwort has compound umbels, with 12–40 smooth rays (stalks), 3–8 cm long, which carry the smaller umbels. These rays are shorter than the stalk (peduncle) below, and they do not become thicker after flowering. At the base of the rays are about five bracts, which are linear to trifid in shape. These umbels are either terminal (at the top of the step) or lateral (in the leaf axils). The small umbellules, which are 5–10 cm in diameter, have 6 or more bracteoles at their base and numerous flowers on short pedicels. The flowers are white, almost actinomorphic  with five subequal petals, the outer ones being slightly larger. There are also five conspicuous sepals which are triangular, sharply pointed, and persistent. The terminal umbels have mostly bisexual flowers; the lateral ones have mostly male flowers. The flowers have five stamens and (if present) two styles, with an enlarged base forming a structure called a stylopodium. The cylindrical fruits are 4–6 mm long, with styles measuring 2 mm in length. This species usually flowers in June and July in northern Europe. Taxonomy. Although hemlock water-dropwort has been recognised as a distinct plant for centuries, the modern definition was  worked out by Artedius in the early 18th century, and the name was published by Linnaeus in 1753 in Species Plantarum. It has several synonyms (i.e. other authors have named the same plant, but the Linnaean name for it stands), including "Phellandrium plinii" Bubani (1899), "Oenanthe macrosciadia" Willk. (1852) and "O. gallaecica" Pau & Merino (1904). A full list can be found in the Synonymic Checklists of the Plants of the World. It has no subspecies, but numerous varieties have been named, none of which is in common use today. There are no recorded hybrids. Its chromosome number is 2n =  22 (based on British specimens). Distribution and habitat. Hemlock water-dropwort is native to the British Isles, although only common locally in the south and west and rarer or absent elsewhere. The native range extends from Britain, Belgium and Netherlands down to southwestern Europe, the western Mediterranean and North Africa. It grows in shallow freshwater in streams, marshes, lakes, ponds, canals, wet woodland and on riverbanks as well as in rocky coastal streams. The plant is usually a calcifuge, and as a lowland species it nearly always occurs below 300 m. Identification. Hemlock water-dropwort is easily separated from the  other water-dropworts in Britain by its greater size, its broad, flat leaflets, and the long, thin bracts on the primary umbels. It is more likely to be confused with species in other genera, including perhaps cowbane or greater water-parsnip. The former has no bracts and latter has upper leaves which are just once pinnate, while hemlock water-dropwort always has at least ternate leaflets (divided into three parts). Toxicity. The toxic principle in the plant is oenanthotoxin, a polyunsaturated higher alcohol that is a potent convulsant and resembles cicutoxin, the toxic constituent in hemlock. The plant is very  poisonous to humans and livestock and can cause imminent death if poisoning is left untreated after ingestion. Symptoms in livestock include increased salivation, dilated pupils, respiratory distress, and convulsions. Cattle poisoning from this plant occurs sporadically. For example, several cases were reported during the 1995 drought in the West Country, England. Due to the shortage of grass in the fields, the cattle were driven to graze by ditches where hemlock water-dropwort grew. More occasional instances of human poisoning have also been reported, in which the plant roots consumed were mistaken for wild parsnip and the leaves for wild celery . Symptoms in humans include nausea, vomiting, seizures, hallucinations, ataxia, and respiratory distress. The roots are the most toxic part of the plant, with toxin concentrations being highest in winter and spring. Boiling the roots seems to both lessen the severity of the symptoms and prolong the delay after which they appear following ingestion. Uses and in culture. Scientists at the University of Eastern Piedmont in Italy wrote that they had identified "Oenanthe crocata" as the plant responsible for producing the sardonic grin. This plant is a possible candidate for the "sardonic herb", which was a neurotoxic plant referred to in  ancient histories. It was purportedly used for the ritual killing of elderly people and criminals in Nuragic Sardinia. The subjects were intoxicated with the herb and then dropped from a high rock or beaten to death. The essential oils from the seeds of "O. crocata" have been shown to have moderate antibacterial effect against "Streptococcus faecalis" and "Bacillus lentus". The oils are also anti-inflammatory, antioxidant and anti-fungal (esp. against "Cryptococcus neoformans"), and they have been suggested for use in counteracting inflammatory diseases. Similar species. The hemlock water-dropwort shares a genus with many other superficially similar European water -dropworts, all of which are poisonous but not deadly.