(M61) But why should the crown of oak have ceased to be the badge of victory? and why should a wreath of laurel have taken its place? The abandonment of the oak crown may have been a consequence of the disappearance of the oak itself from the neighbourhood of Delphi; in Greece, as in Italy, the deciduous trees have for centuries been retreating up the mountain sides before the advance of the evergreens.(219) When the last venerable oak, the rustling of whose leaves in the breeze had long been listened to as oracular, finally succumbed through age, or was laid low by a storm, the priests may have cast about for a tree of another sort to take its place. Yet they sought it neither in the lower woods of the valley nor in the dark forests which clothe the upper slopes of Parnassus above the frowning cliffs of Delphi. Legend ran that after the slaughter of the dragon, Apollo had purged himself from the stain of blood in the romantic Vale of Tempe, where the Peneus flows smoothly in a narrow defile between the lofty wooded steeps of Olympus and Ossa. Here the god crowned himself with a laurel wreath, and thither accordingly at the Festival of Crowning his human representative went to pluck the laurel for his brows.(220) The custom, though doubtless ancient, can hardly have been original. We must suppose that in the beginning the dragon-guarded tree, whether an oak or a laurel, grew at Delphi itself. But why should the laurel be chosen as a substitute for the oak? Mr. A. B. Cook has suggested a plausible answer. The laurel leaf resembles so closely the leaf of the ilex or holm-oak in both shape and colour that an untrained observer may easily confuse the two. The upper surface of both is a dark glossy green, the lower surface shews a lighter tint. Nothing, therefore, could be more natural than to make the new wreath out of leaves which looked so like the old oak leaves that the substitution might almost pass undetected.(221) Whether at Thebes, as at Delphi, the laurel had ousted the oak from the place of honour at the festival of the Slaying of the Dragon, we cannot say. The oak has long disappeared from the low hills and flat ground in the neighbourhood of Thebes, but as late as the second century of our era there was a forest of ancient oaks not many miles off at the foot of Mount Cithaeron.(222)