The leaves of the common poison-ivy are extremely variable, the three leaflets being the only constant character. It is impossible to describe the great range of variation in the shape or lobing of the leaflets. A study of the leaf patterns, especially the six shown in figure 6, will give a fair range of types, although other forms may be found. One plant may have a large variety of forms of leaves or it may have all leaves of about the same general character. The most common type of leaf having leaflets with even margins is shown in figure 6, _D_, and one with leaflets having slightly lobed margins is shown in figure 6, _E_. The other forms shown in figure 6 are not quite so widespread, but may be the usual type throughout some areas. _Figure 8._--Common poison-ivy, about natural size: _A_, Flowers; _B_, mature fruit. Most of the vines or shrubs of poison-ivy produce some flowers that are always in clusters arising on the side of the stem immediately above a leaf. The flowers are rather inconspicuous among the leaves, as may be noted in figure 7, but they are in quite distinct clusters, as shown in figure 8, _A_. Frequently the flowers do not develop or are abortive and no fruit is produced. When fruits do develop they serve as a positive way of identifying the plant. The berries are not easily confused with the fruits of other plants. They are white and waxy in appearance and have rather distinct lines marking the outer surface, as the segments appear in a peeled orange. These lines may be noted in figure 8, _B_, which shows dense clusters of mature fruit about natural size. Some forms of the poison-ivy have the fruit covered with fine hair, giving it a kind of downy appearance; however, in the more common form the fruits are entirely smooth. The fruit is especially helpful in identifying plants late in fall, in winter, and early in spring, when the leaves are not present. _Figure 9._--The shaded area is the region where the eastern oakleaf form of poison-ivy is likely to occur. Other forms also may be in the same region. OAKLEAF POISON-IVY Of the several kinds of poison-ivy, the oakleaf form occurring in the Eastern and Southern States is more distinctive than some other types. Some people know it as oakleaf ivy while others call it poison-oak, a name more commonly used for the western species discussed later. Botanists have not always agreed upon the scientific name to be applied to this form; however, they now use the name _Rhus toxicodendron_. Some botanists have used the Latin names _R. quercifolia_, while others used the name _Toxicodendron quercifolium_, both of which are more descriptive of the oakleaf form, as the generic name of the oak is _Quercus_. The area where the oakleaf form may occur, from New Jersey to Texas, is outlined in the map shown in figure 9. The common poison-ivy also occurs in some form throughout many parts of this same area.