Amongst the innumerable sources from which the nations of antiquity professed to derive knowledge of futurity and practical guidance in the affairs of life the tree held a very prominent place. Tree-oracles formed, indeed, the natural corollary of tree-worship, and their number and popularity provide additional testimony to the genuineness and extent of the ancient belief that certain trees were tenanted by a supernatural essence. For it was as “animated demoniac beings,” to use Robertson Smith’s phrase, that trees possessed oracular virtue. It was the god dwelling in them who produced the mysterious rustlings and movements of the branches, from which the responses were interpreted by the attendant priests. But according to the ancient view the tree derived a further title to its oracular prestige from its connection by means of its roots with the under-world, the mysterious abode of departed spirits, in whom wisdom and knowledge of the future were supposed to be vested. Thus the special prophetic power attributed to the variety of oak (probably the _Quercus esculus_) which grew at Dodona was ascribed by later writers to the fact that its roots pierced the earth more deeply than those of other trees, reaching down even to Tartarus (_tantum radice in Tartara_).[201] It was from this under-world that Saul summoned Samuel, and it was in the hope of obtaining help from the spirit of some dead hero by means of a dream, that men were wont to pass the night at his tomb or his temple. The modern Arabs who still worship certain sacred trees, as the place where angels or _jinni_ descend, believe that a sick man who sleeps under such a tree will receive counsel in a dream for the restoration of his health.[202]