The hilltops likewise are chiefly open, but forest of the hillsides encroaches onto them for as much as 100 yards in some places. The slopes between the hilltops and the valleys are almost everywhere wooded, but the aspect of the woods changes from place to place. Subdivisions on a vertical scale, might be recognized as follows: the upper limestone outcrop (Plattsmouth member) at the hilltop; the usually steep slope strewn with rocks, between the upper and lower (Toronto) limestone outcrop; the lower limestone outcrop; an almost level terracelike formation often approximately 50 feet wide a few feet below the level of the Toronto limestone; the slope below the terrace, variable in steepness, exposure, and soil type, and usually several times more extensive than the first four subdivisions combined. Along both the upper and lower outcrops, elm and hackberry are especially prominent. Chestnut oak is abundant along the outcrops and on the rocky slope between them in some situations. Ash grows abundantly on some upper slopes but there are few growing on the upper outcrop. On the terrace, elm, ash, hackberry, honey locust, coffee-tree and black oak are abundant. On the lower slopes grow most of the blackjack oaks, post oaks, red oaks and mulberries. Even greater differences in the local aspect of woodland on the hillsides are caused by slope exposure. On south facing slopes, especially, the woodland is noticeably different from that in other situations, and of more xeric aspect. The climax species, _Quercus Muehlenbergii_, _Q. rubra_, _Q. velutina_ and _Carya ovata_ are almost totally absent. Such trees as are present are of small to medium size. They are mostly red elm, American elm, walnut, honey locust, hackberry, and osage orange, with dogwood (_Cornus Drummondii_) and plum (_Prunus americanus_) forming dense thickets. Occasional patches of prairie grasses remain in more exposed situations where they have not been shaded out. These, together with the small size of most of the trees, indicate that the south slopes have become wooded rather recently, and originally were prairie. Nevertheless, the small remaining groves of blackjack oak and post oak are on slopes that face south, southeast, or southwest, and probably under original conditions they occupied these situations, separate from the forests of other hardwoods. Slopes facing east, west, and north, are more similar in relative abundance of various kinds of trees, and they do not differ much from hilltop edges that are wooded. Chestnut oak and hickory are most abundant on north slopes, and ash occurs mainly on north slopes. Table 1.--Percentages of Larger Trees (a Foot or More in Trunk Diameter) on Different Slope Exposures.