As in other ivy the leaves consist of three leaflets with much irregularity in the manner of lobing, especially of the two lateral leaflets. The Latin name _dirersiloba_ refers to the irregularity occurring in the shapes of the leaves on different plants and on the same plant or even irregularity in the lobing of leaflets of the same leaf. Sometimes lobes occur on both sides of a leaflet, thus giving it somewhat the semblance of an oak leaf. The middle or terminal leaflet is more likely to be lobed on both sides and resembles an oak leaf more than the other two. A study of the leaves shown in figures 15 and 17 shows the variation in lobing. Some plants may have leaflets with an even margin and no lobing whatsoever, as those in figure 15, _B_. The surface of the leaves is usually glossy and uneven, so that they have a thick leathery appearance. _Figure 19._--A large poison sumac shrub about 15 feet tall, growing on the edge of a swamp. The flowers are borne in clusters on slender stems diverging from the axis of the leaf, as may be noted in figure 17, _C_. The individual flowers are greenish white and about one-fourth inch across. The cluster of flowers matures into greenish or creamy-white berrylike fruits about mid-October. These are about the size of small currants and are much like other poison-ivy fruits, having a smooth greenish-white glossy surface striped somewhat like the segments of a peeled orange. Many plants bear no fruit, although others produce it in abundance, as shown in figure 18, _A_. The fruits are not always spherical, but sometimes have a somewhat flattened appearance, as is shown in figure 18, _B_. They remain on the plants throughout fall and winter and are quite helpful in identifying poison-oak in seasons after the leaves have fallen. _Figure 20._--The shaded area shows the region where poison sumac is likely to occur in bogs or swamps, although isolated plants are sometimes found in dry soil. POISON SUMAC Poison sumac grows as a coarse woody shrub or small tree (fig. 19) and never in the vinelike form of its poison-ivy relatives. This plant is known also as swamp sumac, poison elder, poison ash, poison dogwood, and thunderwood. It does not have variable forms, such as occur in poison-oak or poison-ivy, and botanists agree to call it _Rhus vernix_. The area in the Eastern States where it is likely to be found is chiefly eastward from eastern Minnesota, northeastern Illinois, Indiana, central Kentucky and Tennessee, and southeastern Texas, as shown on the shaded area of the map, figure 20. This shrub is usually associated with swamps and bogs, and the most typical growth occurs along the margin of an area of wet acid soil. _Figure 21._--Small branch of poison sumac with six compound leaves.