from Encyclopedia Brittanica online:

- Lavender -

    Any plant of the genus Lavandula, comprising about 20 species of the mint family Labiatae, native to countries bordering on the Mediterranean. English lavender (L. officinalis, L. spica, or L. vera) is cultivated widely for its essential oil and for its narrow fragrant leaves and spikes of purple flowers that are dried and used in sachets. French lavender (L. stoechas) and L. lanata, native to Spain, are also widely cultivated. The ancient Romans used lavender in their baths, and the dried flowers have long been used to scent chests and closets.

    Lavender is a small evergreen shrub with gray-green, hoary, linear leaves, and light-purple flowers sparsely arranged on spikes at the tips of long, bare stalks. The fragrance of the plant is caused by shining oil glands imbedded among tiny star-shaped hairs with which the flowers, leaves, and stems are covered. The plants in cultivation do not produce seed, and propagation is by slips or by dividing the roots. In Britain and the United States, lavender is cultivated for its essential oil, while in the south of Europe the flowers are an object of trade.

    Lavender oil is obtained by distillation of the flowers and is used chiefly in fine perfumes and cosmetics. It is a colourless or yellow liquid, the fragrant constituents of which are linalyl acetate, linalool, pinene, limonene, geraniol, and cineole. Lavender water, a solution of the essential oil in alcohol with other added scents, is used in a variety of toilet preparations.

    Spike oil, or spike lavender oil, is distilled from a somewhat inferior grade of lavender having grayer leaves. Oil of spike is used in painting on porcelain, in soap manufacture, and to scent other products.