Commerce—The growing trade in grass oil is exemplified in a striking manner by the following statistics. The export of Citronella Oil from Ceylon in 1864 was 622,000 ounces, valued at £8230. In the Ceylon Blue Book, the exports for 1872 are returned thus:—
| To the United Kingdom | 1,163,074 | ounces |  | 1,595,257 ounces.[2711] |
| British India | 5,713 | ” | ||
| United States of North America | 426,470 | ” |
In 1875 the oil shipped from Ceylon to the United Kingdom was valued at 42,871 rupees, that sent to other foreign countries at 45,871 rupees, to British possessions 660 rupees (one rupee equal to about 2s.).
Oil of Lemon Grass, which is a more costly article and less extensively produced, was exported from Ceylon during the same year to the extent of 13,515 ounces, more than half of which quantity was shipped to the United States. There are no analogous statistics for these two oils from Singapore, where, as stated at [p. 726], they are now largely manufactured.
By the official Report on the External Commerce of Bombay, published in 1867, we find that during the year ending 31 March, 1867, Grass Oil [i.e. Ginger Grass or Rúsa Oil] was exported thence to the amount of 41,643 lb. This oil is shipped to England and to the ports of the Red Sea.
Uses—Grass oils are much esteemed in India as an external application in rheumatism. Rúsa oil is said to stimulate the growth of the hair. Internally, grass oil is sometimes administered as a carminative in colic; and an infusion of the leaves of lemon grass is prescribed as a diaphoretic and stimulant. In Europe and America the oils are used almost exclusively by the soapmakers and perfumers.[2712]
But the most remarkable use made of any grass oil is that for adulterating Attar of Rose in European Turkey. The oil thus employed is that of Andropogon Schœnanthus L. ([see p. 725]); and it is a curious fact that its Hindustani name is closely similar in sound to the word rose. Thus under the designation Rusa, Rowsah, Rosa, Rosé, Roshé,[2713] it is exported in large quantities from Bombay to the ports of Arabia, probably chiefly to Jidda, whence it is carried to Turkey by the Mahommedan pilgrims. In Arabia and Turkey, it appears under the name Idris yàghi, while in the attar-producing districts of the Balkan it is known, at least to Europeans, as Geranium Oil or Palmarosa Oil. Before being mixed with attar, the oil is subjected to a certain preparation, which is accomplished by shaking it with water acidulated with lemon juice, and then exposing it to the sun and air. By this process, described by Baur,[2714] the oil loses a penetrating after-smell, and acquires a pale straw-colour. The optical and chemical differences between grass oil thus refined and attar of rose are slight and do not indicate a small admixture of the former. If grass oil is added largely to attar, it will prevent its congealing.
Adulteration—The grass oil prepared by the natives of India is not unfrequently contaminated with fatty oil.
Other Products of the genus Andropogon.
Herba Schœnanthi vel Squinanthi, Juncus odoratus, Fœnum Camelorum.