Dr. Evans argues that “the original holy object within the central triliths of Stonehenge was a sacred tree,” an oak, image of the Celtic Zeus.  The tree and the stones, once associated with ancestor worship, had become symbols of “a more celestial Spirit or Spirits than those of departed human beings."[670] But Stonehenge has now been proved to have been in existence before the arrival of the Celts, hence such a cult must have been pre-Celtic, though it may quite well have been adopted by the Celts.  Whether this hypothetical cult was practised by a tribe, a group of tribes, or by the whole people, must remain obscure, and, indeed, it may well be questioned whether Stonehenge was ever more than the scene of some ancestral rites.

Other trees—­the yew, the cypress, the alder, and the ash, were venerated, to judge by what Lucan relates of the sacred grove at Marseilles.  The Irish Druids attributed special virtues to the hazel, rowan, and yew, the wood of which was used in magical ceremonies described in Irish texts.[671] Fires of rowan were lit by the Druids of rival armies, and incantations said over them in order to discomfit the opposing host,[672] and the wood of all these trees is still believed to be efficacious against fairies and witches.

The Irish bile was a sacred tree, of great age, growing over a holy well or fort.  Five of them are described in the Dindsenchas, and one was an oak, which not only yielded acorns, but nuts and apples.[673] The mythic trees of Elysium had the same varied fruitage, and the reason in both cases is perhaps the fact that when the cultivated apple took the place of acorns and nuts as a food staple, words signifying “nut” or “acorn” were transferred to the apple.  A myth of trees on which all these fruits grew might then easily arise.  Another Irish bile was a yew described in a poem as “a firm strong god,” while such phrases in this poem as “word-pure man,” “judgment of origin,” “spell of knowledge,” may have some reference to the custom of writing divinations in ogham on rods of yew.  The other bile were ash-trees, and from one of them the Fir Bile, “men of the tree,” were named—­perhaps a totem-clan.[674] The lives of kings and chiefs appear to have been connected with these trees, probably as representatives of the spirit of vegetation embodied in the tree, and under their shadow they were inaugurated.  But as a substitute for the king was slain, so doubtless these pre-eminent sacred trees were too sacred, too much charged with supernatural force, to be cut down and burned, and the yearly ritual would be performed with another tree.  But in time of feud one tribe gloried in destroying the bile of another; and even in the tenth century, when the bile maighe Adair was destroyed by Maelocohlen the act was regarded with horror.  “But, O reader, this deed did not pass unpunished."[675] Of another bile, that of Borrisokane, it was said that any house in which a fragment of it was burned would itself be destroyed by fire.[676]