Description—The root is perennial, and tapering, simple, or slightly branched, attaining in a good soil a length of a foot or more, and half an inch to an inch in diameter. Old roots divide at the crown into several heads. The root is fleshy and brittle; externally of a pale brown, internally white, and abounding in an inodorous milky juice of bitter taste. It shrinks very much in drying, losing in weight about 76 per cent.[1448]
Dried dandelion root is half an inch or less in thickness, dark brown, shrivelled with wrinkles running lengthwise often in a spiral direction; when quite dry, it breaks easily with a short corky fracture, showing a very thick white bark, surrounding a woody column. The latter is yellowish, very porous, without pith or rays. A rather broad but indistinct cambium-zone separates the wood from the bark, which latter exhibits numerous well-defined concentric layers. The root has a bitterish taste.
Microscopic Structure—On the longitudinal section, especially in a tangential direction, the brownish zones are seen to contain laticiferous vessels, only about 2 mkm. in diameter. These traverse their zones in a vertical direction, giving off numerous lateral branches, which however remain always confined to their zone. Within each of these zones, the lacticiferous vessels form consequently an anastomosing net. We may say that the root is thus vertically traversed by about 10 to 20 concentric rings of lacticiferous vessels.[1449] They may be made beautifully evident by means of anilin-blue, with which a thin longitudinal section of the fresh root may be moistened. The root must be allowed to partially dry, but only till the milky juice coagulates; the thin slice then energetically absorbs the colouring matter.[1450]
The tissue of the dried root is loaded with inulin, which does not occur in the solid form in the living plant. The woody part of taraxacum root is made up of large scalariform vessels accompanied by parenchymatous tissue, the former much prevailing.
Chemical Composition—The fresh milky juice of dandelion is bitter and neutral, but it soon acquires an acid reaction and reddish brown tint, at the same time coagulating with separation of masses of what has been called by Kromayer (1861), Leontodonium. This chemist, by treating this substance with hot water, obtained a bitter solution yielding an active (?) principle to animal charcoal, from which it was removed by means of boiling spirit of wine. After the evaporation of the alcohol, Kromayer purified the liquid by addition of basic acetate of lead, saturation of the filtered solution with sulphuretted hydrogen and evaporation to dryness. The residue then yielded to ether an acrid resin, and left a colourless amorphous mass of intensely bitter taste, named by Kromayer Taraxacin. Polex (1839) obtained apparently the same principle in warty crystals; he simply boiled the milky juice with water and allowed the concentrated decoction to evaporate.
The portion of the “Leontodonium,” not dissolved by water, yields to alcohol a crystalline substance, Kromayer’s Taraxacerin, C₈H₁₆O. It resembles lactucerin and has in alcoholic solution an acrid taste. How far the medicinal value of dandelion is dependent on the substances thus extracted, is not yet known.
Dragendorff (1870) obtained from the root gathered near Dorpat in October and dried at 100° C., 24 per cent. of Inulin and some sugar. The root collected in March from the same place yielded only 1·74 per cent. of inulin, 17 of uncrystallizable sugar and 18·7 of Levulin. The last named substance, discovered by Dragendorff, has the same composition as inulin, but dissolves in cold water; the solution tastes sweetish, and is devoid of any rotatory power. Inulin is often to be seen as a glistening powder when extract of taraxacum is dissolved in water.
T. and H. Smith of Edinburgh (1849) have shown that the juice of the root by a short exposure to the air undergoes a sort of fermentation which results in the abundant formation of Mannite, not a trace of which is obtainable from the perfectly fresh root. Sugar which readily underwent the vinous fermentation was found by the same chemists in considerable quantity.
The leaves and stalks of dandelion (but not the roots) were found by Marmé (1864) to afford the Inosite, C₆H₁₂O + 2 OH.
The root collected in the meadows near Bern immediately before flowering, carefully washed and dried at 100° C., yielded us 5·24 per cent. of ash, which we found to consist of carbonates, phosphates, sulphates, and in smaller quantity also of chlorides.