But some plants, as we have already pointed out, were credited with the magic property of revealing the presence of witches, and of exposing them engaged in the pursuit of plying their nefarious calling.  In this respect the St. John’s wort was in great request, and hence it was extensively worn as an amulet, especially in Germany on St. John’s Eve, a time when not only witches by common report peopled the air, but evil spirits wandered about on no friendly errand.  Thus the Italian name of “devil-chaser,” from the circumstance of its scaring away the workers of darkness, by bringing their hidden deeds to light.  This, moreover, accounts for the custom so prevalent in most European countries of decorating doorways and windows with its blossoms on St. John’s Eve.  In our own country Stowe[20] speaks of it as its having been placed over the doors together with green birch, fennel, orpine, and white lilies, whereas in France the peasantry still reverence it as dispersing every kind of unseen evil influence.  The elder was invested with similar properties, which seem to have been more potent than even those attributed to the St. John’s wort.  According to an old tradition, any baptized person whose eyes were anointed with the green juice of its inner bark could see witches in any part of the world.  Hence the tree was extremely obnoxious to witches, a fact which probably accounts for its having been so often planted near cottages.  Its magic influence has also caused it to be introduced into various rites, as in Styria on Bertha Night (January 6th), when the devil goes about in great force.[21] As a safeguard, persons are recommended to make a magic circle, in the centre of which they should stand with elder-berries gathered on St. John’s Night.  By so doing the mystic fern seed may be obtained, which possesses the strength of thirty or forty men.  In Germany, too, a species of wild radish is said to reveal witches, as also is the ivy, and saxifrage enables its bearer to see witches on Walpurgis Night.

But, in spite of plants of this kind, witches somehow or other contrived to escape detection by the employment of the most subtle charms and spells.  They generally, too, took the precaution of avoiding such plants as were antagonistic to them, displaying a cunning ingenuity in most of their designs which it was by no means easy to forestall.  Hence in the composition of their philtres and potions they infused the juices of the most deadly herbs, such as that of the nightshade or monkshood; and to add to the potency of these baleful draughts they considered it necessary to add as many as seven or nine of the most poisonous plants they could obtain, such, for instance, as those enumerated by one of the witches in Ben Jonson’s “Masque of Queens,” who says:—­

  “And I ha’ been plucking plants among
  Hemlock, Henbane, Adder’s Tongue;
  Nightshade, Moonwort, Libbard’s bane,
  And twice, by the dogs, was like to be ta’en.”