Margins of leaves with sharp teeth. Petioles glabrous beneath 1 P. americana. Petioles more or less pubescent all around. 2 P. americana var. lanata. Margins of leaves with blunt or crenate teeth. Teeth of center of leaves about 10 per cm.; calyx lobes glandular; fruit more than 10 mm. in diameter. Principal leaves of fruiting branches generally more than 4 cm. broad; flowers white and generally more than 17 mm. wide. 3 P. nigra. Principal leaves of fruiting branches generally less than 4 cm. broad; flowers white which on age show a tinge of pink and generally less than 17 mm. wide. 4 P. hortulana. Teeth of center of leaves about 20 per cm.; calyx lobes glandless; fruit less than 10 mm. in diameter. 5 P. pennsylvanica. Flowers in racemes, appearing after the leaves on twigs of the present year 6 P. serotina. =1. Prunus americàna= Marshall. Wild Red Plum. Plate 99. Small trees with crooked branches; bark of old trees exfoliating in irregular plates; twigs smooth; leaves obovate or oval, 5-9 cm. long, 2.5-5 cm. wide, narrowed or sometimes rounded at the base, acuminate at apex, margins sharply serrate or doubly serrate, glabrous above and smooth below, or hairy on the veins and sometimes more or less pubescent over the whole under surface, inner surface of petiole more or less hairy and sometimes bearing one or two glands; flowers appear in April or May before or with the leaves in clusters of 2-4 or sometimes singly, about 2 cm. in diameter, calyx smooth or with some hairs near the base of the lobes which are pubescent within and smooth or hairy without, lobes entire or cut-toothed above the middle, glandless or with inconspicuous glands; fruit ripens in August or September, usually globose, about 2 cm. in diameter, red; stone doubly convex, oval to nearly orbicular, surface usually smooth. [Illustration: Plate 99. PRUNUS AMERICANA Marshall. Wild Red Plum. (× 1/2.)] =Distribution.=--Massachusetts to Florida, west to Manitoba and south to New Mexico. Found throughout Indiana. While it has a general distribution, it is not generally distributed through the forests, but is local in colonies in low grounds along streams or in low places in the forest. In the southern counties it is found on the ridges and commonly about the basins of sink-holes. Large single trees may be found but they are usually surrounded by many smaller ones which are root shoots. From this habit of the tree to produce root shoots large colonies are formed which has given rise to the term "plum thickets."