Source, Etc

The common or spotted hemlock, Conium maculatum, Linne (N.O. Umbelliferoe), is a biennial plant widely spread throughout temperate Europe, and generally distributed over Great Britain. It was in all probability the plant employed by the Greeks in the preparation of poisonous draughts, and was much used in Anglo-Saxon medicine, but latterly has lost much of its reputation owing to the uncertain action of preparations made from it. The herb is cultivated for medicinal use, but wild plants are also collected.

Description

The plant produces, usually in its second year, an erect, cylindrical, glabrous, hollow stem, reaching a height of 1.5 to 2 metres, the lower part of which bears purplish spots which, however, usually disappear on drying.

The leaves are dark green on the upper, paler on the under surface, quite glabrous, and attached to the stem by amplexicaul petioles. The lower are large and decompound, attaining 50 cm. in length, the upper being less divided; the ultimate segments are ovate or lanceolate, and acute, terminating in smooth, colourless, horny points (fig. 105, a).

The umbels are about twelve-rayed, and provided with both general and partial involucres, the latter consisting of three short, lanceolate bracts directed outwards. The fruits are broadly ovate and characterised by the irregular, crenate ridges and grooved endosperm. (Compare 'Hemlock Fruits.')

Description 162Description 163FIG. 105.   Portion of leaf of a, Conium maculatum; b, Anthriscus sylvestris; c, AEthusa Cynapium. Magnified 2 diam. (Vogl.)

FIG. 105. - Portion of leaf of a, Conium maculatum; b, Anthriscus sylvestris; c, AEthusa Cynapium. Magnified 2 diam. (Vogl).

The plant has a bitterish taste and unpleasant odour, especially when crushed; the addition of solution of potash produces a strong, disagreeable odour of mice.

The student should observe

(a) The glabrous, spotted hollow stem,

(b) The much divided leaves, which are paler on the under surface, quite glabrous, the ultimate divisions terminating in smooth colourless points,

(c) The general and partial involucres,

(d) The crenate ridges and grooved endosperm of the fruit.

Constituents

Hemlock herb contains coniine and conhydrine. These alkaloids are present in both stem and leaves in largest quantity when the plant is in full flower, the stem then containing 0.064 per cent., the leaves 0.187 per cent., and the flowers and flower-stalks

0.236 per cent. (Farr and Wright). The herb should therefore be collected when the fruit begins to form (compare p. 111).

Uses

Fresh hemlock herb is used for the preparation of the green extract and juices. These are administered as sedatives in various spasmodic diseases, in asthma, whooping cough, and spasmodic affections of the larynx.

Adulterations

Several indigenous Umbelliferous plants have been mistaken for hemlock, but the characters detailed above are sufficient to ensure the identification of the latter. The following may be particularly alluded to:

Anthriscus Sylvestris, Hoffmann, Wild Chervil

One of the commonest Umbelliferous plants; it has, in common with the other less frequent species of the genus, hairy leaves by which it is easily distinguished from hemlock (fig. 105, b). The involucels are not directed outwards, and the fruit is elongated.

Choerophyllum temulum, Linne, Rough Chervil, also has hairy leaves.

Aethusa Cynapium, Linne, Fool's Parsley

The ultimate divisions of the leaves terminate in short brownish points. The under surface is dark green and glossy, and exhibits a more or less distinct network of veinlets (fig. 105, c). The umbel has no general involucre, and the bracts of the partial involucre are long and narrow. A transverse section of the leaf-stalk examined under the microscope shows on the upper surface a large central cell developed into a trichome.

Oenanthe crocata, Linne, has tuberculated roots; the juice of both stem and roots turns yellow when exposed to the air; very toxic.

Cicuta virosa, Linne, has narrow lanceolate, acute, serrated, leaf-segments.