.
It was long-lived, its foliage was a protection, it supplied food, its
wood was used as fuel, and it was thus clearly the friend of man. For
these reasons, and because it was the most abiding and living thing men
knew, it became the embodiment of the spirits of life and growth.
Folk-lore survivals show that the spirit of vegetation in the shape of
his representative was annually slain while yet in full vigour, that his
life might benefit all things and be passed on undiminished to his
successor.[668] Hence the oak or a human being representing the spirit
of vegetation, or both together, were burned in the Midsummer fires.
How, then, did the oak come to symbolise a god equated with Zeus. Though
the equation may be worthless, it is possible that the connection lay in
the fact that Zeus and Juppiter had agricultural functions, or that,
when the equation was made, the earlier spirit of vegetation had become
a divinity with functions resembling those of Zeus. The fires were
kindled to recruit the sun's life; they were fed with oak-wood, and in
them an oak or a human victim representing the spirit embodied in the
oak was burned. Hence it may have been thought that the sun was
strengthened by the fire residing in the sacred oak; it was thus "the
original storehouse or reservoir of the fire which was from time to time
drawn out to feed the sun."[669] The oak thus became the symbol of a
bright god also connected with growth. But, to judge by folk survivals,
the older conception still remained potent, and tree or human victim
affected for good all vegetable growth as well as man's life, while at
the same time the fire strengthened the sun.

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, wer