The cultivation of sugar has been long carried on in Java, and since the decline of the coffee plantations it has developed into the leading industry of the island. There are experimental stations at Pasuruan, Pekalongan and elsewhere, where attempts are made to overcome the many diseases to which the cane is subject. Many of the mills are equipped with high-class machinery and produce sugar of excellent colour and grain. In 1853-1857 the average crop was 98,094 tons; in 1869-1873, 170,831, and in 1875-1880, 204,678. By 1899-1900 the average had risen to 787,673 tons; and the crops for 1904 and 1905 were respectively 1,064,935 and 1,028,357 tons. Prices fluctuate, but the value of the harvest of 1905 was estimated at about £15,000,000. The cultivation of indigo shows a strange vitality. Under the culture system the natives found this the most oppressive of all the state crops. The modern chemist at one time seemed to have killed the industry by his synthetic substitute, but in every year between 1899 and 1904 Java exported between one million and one and a half million pounds of the natural product. Japan and Russia were the largest buyers. As blue is a favourite colour with the Javanese proper a large quantity is used at home. Tea was first introduced to Java by the Japanese scholar von Siebold in 1826. The culture was undertaken by the state in 1829 with plants from China, but in 1842 they handed it over to contractors, whose attempts to increase their profits by delivering an inferior article ultimately led to the abandonment of the contract system in 1860. In the meantime the basis of a better state of the industry had been laid by the Dutch tea-taster J. J. L. L. Jacobsen of the Nederlandsch Handel Maatschappij, who introduced not only fresh stock, but expert growers from China in 1852-1853. The tea-planters (often taking possession of the abandoned coffee-plantations) have greatly improved the quality of their products. Assam tea was introduced in 1878, and this has rapidly extended its area. The exports increased from 12,110,724 lb. in 1898 to 25,772,564 in 1905. More than half the total goes to the Netherlands; the United Kingdom ranks next, and, far behind both, Russia.