Poison Ivy

or Poison Oak, a poisonous plant of the sumac family. It is a low, erect shrub, or else climbing by rootlets over stumps and stones and ascending trees. It has a three-foliate leaf. Greenish flowers are borne in a loose cluster and are followed by globular, whitish fruit like that of its relative, the swamp sumac or poison elder. The sap of the poison ivy is milky and acrid. The plant may be handled with the callous palm of the hand ordinarily without evil effect, but if it touch a tender spot between the fingers, or the arm, or the leg of a barefoot boy, irritation and painful blisters are apt to occur. The effect is ascribed to an oil produced by the plant. It is most virulent at the flowering season. There is a theory that this inflammation is due not to the acrid juice of the plant, as is the case with the nettle, but to certain parasitic plant germs that reside on the plant. If this theory be true, these germs must fly in the air, for at certain seasons a person working amid poison ivy or passing to leeward of a swamp of sumac is likely to be affected by a painful inflammation of the face, even though there be no actual contact. The poison ivy may be known from the American ivy, an unrelated and harmless climber, for the former has leaflets in threes and white berries, while the latter has leaflets in fives and has bluish black berries. This distinction, and the fact that poison sumac has white berries and not the red berries like its harmless relative, may be held in mind by a clever jingle perpetrated by Gibson: