Figure 24.—Leaves of species of sumac that are often confused: A, Smooth sumac; B, staghorn sumac; C, dwarf sumac; D, poison sumac; E, enlarged portion of dwarf sumac leaf from C, showing the wing margin of the midrib. Poison sumac does not have the winged midrib.
INTRODUCED POISONOUS SUMAC AND RELATED SPECIES
The small Japanese lacquer-tree, although uncommon in the United States, is an introduced species of sumac (Rhus verniciflua) that is quite similar to the native poison sumac. It is native to Japan and China and is the source of Japanese black lacquer. Cases of poisoning hare been traced to contact with lacquered articles. Because of its poisonous properties, this tree should never be planted.
A native shrub or small tree called poison-wood, doctor gum, or coral sumac is commonly found in the pinelands and hummocks of extreme southern Florida, the Keys, and the West Indies. It is much like the poison sumac and closely related to it. Most botanists name it Metopium toxiferum, although previously it was named Rhus metopium, and sometimes metopium is used as its common name. The small tree, or shrub, has the same general appearance as poison sumac. The leaves have the same general appearance, except that there are usually only three to seven leaflets, which are more rounded. The fruits are borne in clusters in the same manner as those of poison sumac ([fig. 22]), but individual fruits are two or three times as large and orange-colored. All parts of the plant are exceedingly poisonous to the touch and cause the same kind of skin irritation as poison-ivy or poison sumac.
[POISONING]
Through experience, many people know that they are susceptible to poisoning by poison-ivy, poison-oak, or poison sumac, while some others either have escaped contamination or have a certain degree of immunity. The extent of immunity appears only relative, and absolute immunity to the toxic principle apparently does not exist. Persons who have shown a degree of immunity upon repeated contact with the plants may develop poisoning on subsequent exposure.
The skin irritant of poison-ivy, poison-oak, and poison sumac is the same toxic agent. It is a nonvolatile phenolic substance called urushiol and is found in all parts of the plant, including roots and fruit. It occurs in great abundance in the plant sap. The danger of poisoning is greatest in spring and summer, when the sap is abundant, and least late in fall or in winter.