Description—The fruit is formed by the union of 8 to 20 carpels, the edges of which are turned inwards and project like partitions towards the interior, yet without reaching the centre, so that the fruit is really one-celled. In the unripe fruit, the sutures of the carpels are distinctly visible externally as shallow longitudinal stripes.
The fruit is crowned with a circular disc, deeply cut into angular ridge-like stigmas in number equal to the carpels, projecting in a stellate manner with short obtuse lobes. Each carpel opens immediately below the disc by a pore, out of which the seeds may be shaken; but in some varieties of poppy the carpel presents no aperture even when fully ripe. The fruit is globular, sometimes flattened below, or it is ovoid; it is contracted beneath into a sort of neck immediately above a tumid ring at its point of attachment with the stalk. Grown in rich moist ground in England, it often attains a diameter of three inches, which is twice that of the capsules of the opium poppy of Asia Minor or India. While growing it is of a pale glaucous green, but at maturity becomes yellowish-brown, often marked with black spots. The outer wall of the pericarp is smooth and hard; the rest is of a loose texture, and while green exudes on the slightest puncture an abundance of bitter milky juice. The interior surface of the pericarp is rugose, and minutely and beautifully striated transversely. From its sutures spring thin and brittle placentæ directed towards the centre and bearing on their perpendicular faces and edges a vast number of minute reniform seeds.
The unripe fruit has a narcotic odour which is destroyed by drying; and its bitter taste is but partially retained.
Microscopic Structure—The outer layer consists of a thin cuticle exhibiting a large number of stomata; the epidermis is formed of a row of small thick-walled cells. Fragments of these two layers, which on the whole exhibit no striking peculiarity, are always found in the residue of opium after it has been exhausted by water.
The most interesting part of the constituent tissues of the fruit is the system of laticiferous vessels, which is of an extremely complicated nature inasmuch as it is composed of various kinds of cells intimately interlaced so as to form considerable bundles.[182] The cells containing the milky juice are larger but not so much branched as in many other plants.
Chemical Composition—The analyses of poppy heads present discrepant results with regard to morphine. Merck and Winckler detected it in the ripe fruit to the extent of 2 per cent., and it has also been found by Groves (1854) and by Deschamps d’Avallon (1864). Other chemists have been unable to find it.
In recent pharmacopœias poppy heads are directed to be taken previous to complete maturity, and both Meurein and Aubergier have shown that in this state they are richer in morphine than when more advanced. Deschamps d’Avallon found them sometimes to contain narcotine. He also obtained mucilage perceptible by neutral acetate of lead, ammonium salts, meconic, tartaric, and citric acid, the ordinary mineral acids, wax, and lastly two new crystalline bodies, Papaverin, and Papaverosine. The former is not identical with Merck’s alkaloid of the same name; although nitrogenous and bitter, it has an acid reaction (?), yet does not combine with bases. It yields a blue precipitate with a solution of iodine in iodide of potassium.
Papaverosine on the other hand is a base to which sulphuric acid imparts a violet colour, changing to dark yellowish-red on addition of nitric acid.
In ripe poppy heads, Hesse (1866) found Rhœadine. Groves in 1854 somewhat doubtfully announced the presence of Codeine. Fricker[183] stated to have obtained from the capsules 0·10 per cent. of alkaloid, and Krause[184] was able to prove the presence of traces of morphine, narcotine, and meconic acid. Ripe poppy capsules (seeds removed) dried at 100° C. afforded us 14·28 per cent. of ash, consisting chiefly of alkaline chlorides and sulphates, with but a small quantity of phosphate.
Production—Poppies are grown for medicinal uses in many parts of England, mostly on a small scale. The large and fine fruits (poppy heads) are usually sold entire; the smaller and less slightly are broken and the seeds having been removed are supplied to the druggist for pharmaceutical preparations. The directions of the pharmacopœia as to the fruit being gathered when “nearly ripe” does not appear to be much regarded.