The plant varies in stature, foliage, and in the size and form of its fruits; but all the forms belong apparently to a single species.
History—Fennel was used by the ancient Romans, as well for its aromatic fruits, as for its edible succulent shoots. It was also employed in Northern Europe at a remote period, as it is constantly mentioned in the Anglo-Saxon medical receipts, which date as early at least as the 11th century. The diffusion of the plant in Central Europe was stimulated by Charlemagne, who enjoined its cultivation on the imperial farms. Fennel shoots (turiones fœnuculi), fennel water, and fennel seed, as well as anise, are all mentioned in an ancient record[1177] of Spanish agriculture dating a.d. 961.
Description—The fennel fruits of commerce, commonly called Fennel Seeds, are of several kinds and of very different pecuniary value. The following are the principal sorts:—
1. Sweet Fennel,—known also as Roman Fennel, is cultivated in the neighbourhood of Nîmes in the south of France. The plant is a tall perennial with large umbels of 25 to 30 rays.[1178] As the plants grow old, the fruits of each succeeding season gradually change in shape and diminish in size, till at the end of 4 or 5 years they are hardly to be distinguished from those of the wild fennel growing in the same district. This curious fact, remarked by Tabernæmontanus (1588), was experimentally proved by Guibourt.[1179]
The fruits of Sweet Fennel as found in the shops are oblong, cylindrical, about ⁴/₁₀ of an inch in length by ⅒ in diameter, more or less arched, terminating with the two-pointed base of the style, and smooth on the surface. Each pericarp is marked by 5 prominent ridges, the lateral being thicker than the dorsal. Between the ridges lie vittæ, and there are two vittæ on the commissural surface,—all filled with dark oily matter. The fruits seen in bulk have a pale greenish hue; their odour is aromatic, and they have a pleasant, saccharine, spicy taste.
2. German Fennel, Saxon Fennel, produced especially near Weissenfels in the Prussian province of Saxony; the fruits are ²/₁₀ to ¼ of an inch long, ovoid-oblong, a little compressed laterally, slightly curved, terminating in a short conical stylopodium; they are glabrous, of a deep brown, each mericarp marked with 5 conspicuous pale ridges, of which the lateral are the largest. Seen in bulk, the fruits have a greenish brown hue; they have an aromatic saccharine taste, with the peculiar smell of fennel.
3. Wild or Bitter Fennel (Fenouil amer), collected in the south of France, where the plant grows without cultivation. They are smaller and broader than those of the German Fennel, being from ⅕ to ⅙ of an inch long by about ¹/₁₅ of an inch wide. They have less prominent ridges and at maturity are a little scurfy in the furrows and on the commissure. Their taste is bitterish, spicy, and strongly fennel-like. The essential oil (Essence de Fenouil amer) is distilled from the entire herb.
4. Indian Fennel.—A sample in our possession from Bombay resembles Sweet Fennel, but the fruits are not so long, and are usually straight. The mother plant of this drug is F. Panmorium DC., now regarded as a simple variety of F. vulgare Gärtn.
Microscopic Structure—The most marked peculiarity of fennel is exhibited by the vittæ, which are surrounded by a brown tissue. The latter is made up of cells resembling the usual form of cork-cells. In Sweet Fennel the vittæ are smaller than in the German fruit; in the transverse section of the latter, the largest diameter of these ducts is about 200 mkm.
Chemical Composition—The most important constituent of fennel fruits is the volatile oil, which is afforded both by the Sweet and the German fennel to the extent of about 3½ per cent.