From the wood of the _Juniperus oxycoedrus_; an empyreumatic oil resembling liquid pitch, is obtained by dry distillation, this being named officinally, _Huile de cade_, or _Oleum cadinum_, otherwise "Juniper tar." It is found to be most useful as an external stimulant for curing psoriasis and chronic eczema of the skin. A recognised ointment is made with this and yellow wax, _Unguentum olei cadini_. In Italy stables are popularly thought to be protected by a sprig of Juniper from demons and thunderbolts, just as we suppose the magic horseshoe to be protective to our houses and offices. [296] KNAPWEED (The Lesser). Black Knapweed, the _Centaurea nigra_, is a common tough-stemmed composite weed growing in our meadows and cornfields, being well known by its heads of dull purple flowers, with brown, or almost black scales of the outer floral encasement. It is popularly called Hard heads, Loggerheads, Iron heads, Horse knob, and Bull weed. Dr. Withering relates that a decoction made from these hard heads has afforded at least a temporary relief in cases of diabetes mellitus, "by diminishing the quantity of urine, and dispelling the sweetness." Its chief chemical constituent _enicin_, is identical with that of the Blessed thistle, and the Blue bottle, and closely resembles that of the Dandelion. It has been found useful in strengthless indigestion, especially when this is complicated with sluggish torpor of the liver. From half to one ounce of the herb may be boiled in eight fluid ounces of water, and a small wineglassful be taken for a dose twice or three times a day. In Bucks young women make use of this Knapweed for love divination:-- "They pull the little blossom threads From out the Knotweed's button beads, And put the husk with many a smile In their white bosoms for a while; Then, if they guess aright, the swain Their love's sweet fancies try to gain, 'Tis said that ere it lies an hour 'Twill blossom with a second flower." LAVENDER.