Part 17

The leaf is pinnate, or feather-like with 18 to 28 leaflets; or it is twice-pinnate, consisting of 4 to 7 pairs of pinnae or secondary leaflets, each 6 to 8 inches long and somewhat resembling the leaf of the black locust.

The flowers which appear when the leaves are nearly full-grown are inconspicuous, greenish-yellow and rich in honey. The petals vary from 3 to 5, the stamens are 3 to 10 and the ovary is wooly and one-celled.

The fruit is a pod, 10 to 18 inches long, often twisted, 1 to 1-1/2 inches wide, flat, dark brown or black when ripe and containing yellow sweetish pulp and seeds. The seeds are very hard and each is separated from the others by the pulp. The pods are eaten by many animals, and as the seeds are hard to digest, many are thus widely scattered from the parent tree.

The wood is coarse-grained, hard, strong and moderately durable in contact with the ground. It is used for fence posts and crossties. It should not be confused with the very durable wood of the black locust.

The water locust, Gleditsia aquatica Marsh., is found in river bottoms in southern Illinois, becoming a medium sized tree. It may be known by its short pods, 1 to 2 inches long, with only 2 or 3 seeds.

+REDBUD+ Cercis canadensis L.

THE redbud is a small tree occurring under taller trees or on the borders of fields or hillsides and in valleys throughout the State. It ordinarily attains a height of 25 to 50 feet and a diameter of 6 to 12 inches. Its stout branches usually form a wide flat head.

Leaf, one-fourth natural size. Twig, and flowers, two-thirds natural size.]

The bark is bright red-brown, the long narrow plates separating into thin scales.

The leaves are alternate, heart-shaped, entire 3 to 5 inches long and wide, glossy green turning in autumn to a bright clear yellow.

The conspicuous bright purplish-red, pea-shaped flowers are in clusters along the twigs and small branches and appear before or with the leaves in early spring.

The fruit is an oblong, flattened, many seeded pod, 2 to 4 inches long, reddish during the summer, and often hanging on the tree most of the winter.

The wood is heavy, hard, not strong, rich, dark brown in color, and of little commercial importance. The redbud is cultivated as an ornamental tree and for that purpose might be planted more generally in this State.

The Kentucky coffee-tree, Gymnocladus dioicus K. Koch, though not anywhere a common tree, is found on rich bottom lands throughout the State. The much-divided leaves are 2 to 3 feet long. The pods are 5 to 8 inches long and 1 to 2 inches wide and contain hard seeds 3/4 inch long. It has few qualities to recommend it for ornamental planting.

+BLACK LOCUST+ Robinia pseudoacacia L.

THE black locust is a native to the Appalachian Mountains but has been introduced into Illinois, and now occurs throughout the entire State growing on all soils and under all conditions of moisture except in swamps. It is found generally in thickets on clay banks and waste places or along fence rows.

Leaf, one-third natural size. Twig and flower, two-thirds natural size.]

The twigs and branchlets are armed with straight or slightly curved sharp, strong spines, sometimes as much as 1 inch in length which remain attached to the outer bark for many years. The bark is dark brown and divides into strips as the tree grows older.

The leaves are pinnate, or featherlike, from 6 to 10 inches in length, consisting of from 7 to 19 oblong thin leaflets.

The flowers are fragrant, white or cream-colored, and appear in early spring in graceful pendent racemes. The fruit is a pod from 3 to 5 inches long containing 4 to 8 small hard seeds which ripen late in the fall. The pod splits open during the winter, discharging the seeds. Some seeds usually remain attached to each half of the pod; the pod thus acts as a wing upon which the seeds are borne to considerable distances before the strong spring winds.

The wood is yellow in color, coarse-grained, very heavy, very hard, strong, and very durable in contact with the soil. It is used extensively for fence posts, poles, tree nails, insulator pins and occasionally for lumber and fuel.

The tree is very rapid in growth in youth but short-lived. It spreads by underground shoots and is useful for holding and reclaiming badly gullied lands. The usefulness of the black locust is, however, very greatly limited by the fact that it is subject to great damage from an insect known as the locust borer.

+TREE OF HEAVEN+ Ailanthus altissima Swingle

THIS tree is a native of China but planted in Illinois because of its tropical foliage. It has escaped and become naturalized. It is a handsome, rapid-growing, short-lived tree, attaining a height of 40 to 60 feet, and a trunk diameter of 2 to 3 feet. Its crown is spreading, rather loose and open. The twigs are smooth and thick with a large reddish-brown pith. The winter buds are small, globular and hairy, placed just above the large leaf-scars.

Twig, one-half natural size. Leaf and fruit, one-fourth natural size.]

The leaves are alternate, pinnately compound and one to three feet long. The leaflets number from 11 to 41, are smooth, dark green above, paler beneath, turning a clear yellow in autumn.

The flowers appear soon after the leaves are full grown, on different trees, borne in large upright panicles. They are small yellow-green in color with 5 petals and 10 stamens. The staminate flowers have a disagreeable odor.

The fruit, ripening in October but remaining on the tree during the winter, is a one-seeded samara, spirally twisted, borne in crowded clusters.