YALU, yi'loo, Chosen, a river forming the boundary with Manchuria. In its upper reaches it is known as the Am-nok or Ap-nok. Its source is in the Paik-tu-san, the highest peak (8,000 feet) of the Shan-a-lin Mountains of Manchuria. It flows into Korea Bay, near Wi-ju, after a southwesterly course of about 300 miles, and has numerous tributaries, chief of which is the Chang-jin River. It is navi gable for sea-going vessels 30 miles from its mouth and by smaller vessels 145 miles to Wi wen. On 17 Sept. 1894 its mouth was the scene of the battle in which a Chinese fleet of 12 warships, some of them powerful ironclads, and 16 other vessels, was defeated, with the loss of four vessels, by a Japanese force of 11 war vessels and two others. During the Russo-Japanese War of 1904 its banks wit nessed much skirmishing and fighting. The Japanese have renamed it Oryoku. See MAN CH URIA. .
YAM, a popular name for various species of the genus Diastase° of the family Dio scoreacetr, and loosely applied to certain vani ties of the sweet potato. The true yams be long to a genus consisting of more than 150 species widely distributed throughout the tropics. They have herbaceous, twining or creeping stems; broad, alternate or opposite, usually simple leaves; and small dkecious flowers, followed by three-winged capsular fruits containing winged seeds. The fleshy roots of some species are widely eaten in the tropics. One of the best-known species is D. data, a native of India and the South Sea Islands, hut distributed throughout the tropics.
Its tubers usually attain a length of three feet and a weight of 30 pounds, but specimens three times as large are not uncommon. They are black or brownish externally and pink within, and are rich in starch. When boiled their acridity is dispelled and they become of pleasant flavor. It is claimed that this species is the parent of most of the edible so-called species such as D. saliva, D. aculeata, D rubella, D globose, etc. The air-potato (D. bulhifera) is an Asiatic species cultivated to a small extent in the southern United States, and in conservatories, for its odd, angled tubers, which are borne in the axils of the leaves. They often exceed two pounds in weight and are sometimes eaten like potatoes. The Chinese yam, Chinese potato• or cinnamon vine (D. dr:136(01a), is a native of the Philip pine Islands, whence it has been introduced into the gardens of temperate as well as tropi cal climate< for ornament It bears cinnamon scented white blossoms and aerial tubers which are used for propagation. As far north as New York the plants have proved hardy. an Oriental kind of silkworm (Autherea jama-mai), which feeds on the oak,- and produces a silk, known by th./ same name, with peculiar, but useful qualities. extensively utilized in Japan and somewhat elsewhere. See SILKWORMS.