The following are Frazer’s views on this subject: “The mistletoe was viewed as the seat of life of the oak. The conception of the mistletoe as the seat of life of the oak would naturally be suggested to primitive people by the observation that while the oak is deciduous, the mistletoe which grows on it is evergreen. In winter, the sight of its fresh foliage among the bare branches must have been hailed by the worshippers of the tree as a sign that the divine life which had ceased to animate the branches yet survived in the mistletoe, as the heart of the sleeper still beats when his body is motionless. Hence, when the god had to be killed, when the sacred tree had to be burnt, it was necessary to begin by breaking off the mistletoe, for so long as the mistletoe remained intact, the oak (so people thought) was invulnerable,—all the blows of their knives and axes would glance harmless from its surface. But once tear from the oak its sacred heart, the mistletoe, and the tree nodded to its fall.”—(“The Golden Bough,” James G. Frazer, M. A., London, 1890, vol. ii. pp. 295, 296.)
This train of reasoning would be irrefutable, as it is most logical, were we in a position to be able to say that the excision of the fungus was followed by the felling of the tree; but, unfortunately, that is just what we are not able to determine. As a surmise, there is no impropriety in believing that such excision may have marked the oak for destruction at some future day; but there is no authority that we can produce at this time to justify anything more than a surmise in the premises. That the sacred character of the oak was due to the properties discovered in the mistletoe is quite likely in view of all the facts already presented.
O’Curry, who appears to have known all that was to be learned on the subject of Druidism, admits that the world is in possession of very little that is reliable; he inclines to the view that Druidism was of Eastern origin. (See “Manners and Customs of the Ancient Irish,” Eugene O’Curry, London, Edinburgh, Dublin, and New York, 1873.) He contends that “the Sacred Wand” of the Druids was made of the yew, and not of the oak or mistletoe.—(Idem, vol. ii. p. 194.)
Vallencey did not believe that the Persians were acquainted with the mistletoe; at least, he could not find any name for it in Persian.—(See Major Charles Vallencey, “Collectanea de Rebus Hibernicis,” Dublin, 1774, vol. ii. p. 433.)