The date of the Upanishads, like that of the Vedic writings, is quite uncertain, but the ear liest of them can hardly be dated later than B.C. 600, since their most important ideas ap pear in an advanced and somewhat decayed state in the Buddhist writings. The older Upanishads are the products of Vedic schools. The two most important, the Brhaddranyaka and the Chandogya, belong respectively to the White Ya jur Veda and the Sama-Veda; the Aitareya, Taittiriya, Kalhaka, and Maitray aniya or Hanava belong to schools of the same names. The Kcna and Talavakara Upanishads also belong to the Sania-Veda, the Ha to the White Yajnr Veda, the Suetii§retara and the Maheinorayana to the Black Yajur Veda. A large and indefinite number of Upanishads, of which the It uroJaka, Pra.;:na, and 3./a,n/iikeya are the most important, are counted as belonging to the Atharva-Veda. The most authoritative list counts twenty-seven, hut later Upanishads are generally counted as belonging to the Athar van. A complete list of Upanishads is impos sible, because the term Upanishad does not represent a closed canon, but rather an indef initely extensible type of literature which has not been formally concluded, and which may be continued in the present or future. In 1876 235 Upanishads were enumerated, includ ing apocrypha. one of those actually a Moham medan treatise called Alla Upani.cad. The later Upanishads may be divided into five classes: (1) Pure Vedanta Upanishads, which combine the Vedanta doctrines of the older texts without un due development of the notions of l'Aqa (con centration and abstraction from all mundane matters) or SamnyTisa (asceticism) ; (2) Yoga 'Upanishads, which presuppose the Vedanta ideas, and in addition advise mental concentration upon the sacred syllable Ma (q.v.) ; (3) Samnyssa Upanishads, which recommend and describe a life of asceticism as the practical way of attaining the purpose of the Upanishads; (4) Siva Upan ishads, which interpret the popular god Siva (q.v.) as a personification of the Oman; (5)
Vishnu Upanishads, which interpret Vishnu (q.v.), or one of his avatars (see AVATAR) , as divine or human manifestations of the a t man.
BIBLIOGRAPHY. Editions of individual UpaniBibliography. Editions of individual Upani- shads are extremely numerous in India. A select list is given by iNlacdonell, History of Sanskrit Literature (London, 1900). A convenient edition of 108 Upanishads was edited by Tukaram Tatya (Bombay, 1895). The older Upanishads were translated into English by Max Miller, Sacrcd Books of the East, vols. i., xv. (2d ed., Oxford, 1900). A more scholarly translation is given by Deussen, Scchzig Upanishads des Veda (Leipzig, 1897), who also published the standard discussion of their philosophy, Die Philosophic der Upani shads (ib., 1899), superseding the work of Gough, The Philosophy of the Upanishads (London, 1882). A valuable aid to the study of these texts is Jacob, Concordance to the Principal Upani shads and Bhagaradgitii (Bombay, 1891).
UPAS (Malay //pas, poison), Avtiaris toxi caria. A tree of the Philippine Islands of the natural order Moraeece, to which also belong the breadfruit, mulberry, etc. The fruit is a kind of drupe, covered with fleshy scales. The Ma lays mix the milky juice of this tree with black pepper and the root juices of galenga and ginger for tipping their arrows. The fibre of the bark is sometimes made into cloth, but unless it is thor oughly cleaned garments made of it are said to produce itching. Some botanists believe that the tree whose bark is used for fibre is a distinct species, as other species of this genus are innoc uous. The story of a poison-vale in Java, in which the exhalations of numerous poison trees destroy all animal life, and even all other vege table life, is a mere fable.