But it is far otherwise with another set of plants--the Mistletoe and its allies. There is plenty of romance connected with the mistletoe. Dr. M. T. Masters says as follows: "The origin of the modern custom connected with mistletoe is not very clear. Like many other customs, its original significance is only guessed at. If known, perhaps, the innocent merriment now associated with the plant would be exchanged for a feeling of stern disapproval, and the mistletoe would be banished from our homes. In such a case ignorance is bliss." It will be remembered that all the gods of Iceland were once gathered together so that a general oath might be exacted of every plant "that grew upon the earth," that they would do no harm to Balder the Beautiful. The Mistletoe did not take the oath, because it does not grow upon the earth but upon a tree. Then the enemy fashioned an arrow out of the mistletoe, and killed Balder. There is a modern idea that the story is a myth representing the death of Spring, for a great many similar stories occur in widely distant places. However, it seems pretty certain that the plant was a sacred one to the Druids in the time of the Romans. Ovid speaks of this in the line, "Ad Viscum Druidæ cantare solebant." At their solemn meetings, which were held in remote sacred groves, a Druid clad in white robes cut the mistletoe with a golden sickle. Then, apparently, human sacrifices were offered and a general festival took place. Some remnant of this custom seems to have persisted in Herefordshire until recent times, for the tune "Hey derry down, down down derry" (which means _in a circle move we round the oak_) is supposed to be a relic of the hymn chanted by the Druids when they had found mistletoe on the oak. It was said in the Middle Ages to be a useful cure for apoplexy, madness, and giddiness. That is not at present the general view. Indeed, under present conditions it might conceivably promote the last and even the second of these disorders, though in an agreeable way! The Mistletoe and its allies, Loranthus and Arceuthobium, grow upon the branches of trees like the orchids and gooseberries already mentioned, but they differ altogether in having a special kind of absorbing root which sinks down into the bark until it reaches the wood of the "host" tree. The sap running up the tree is then tapped by this root, and goes to supply the mistletoe with water and salts in solution. It has, however, its own green leaves. Thrushes eat the berries of the mistletoe; they will be left upon a branch with the _guano_; as the latter dries up, the seed is drawn to the underside of the branch, and sticks in a crack or crevice; it then sends the sinker-root mentioned above into the branch.