The name pin oak is said to belong to this tree because of a peculiarity of its branches. They leave the trunk and the larger limbs at nearly right angles, and criss-cross in all directions, resembling pins thrust into the wood, and bristling outward at every angle. The crowding to which they are subjected kills many of them as the tree reaches middle age, but the stubs do not drop quickly, and as many of the characteristic pins appear to be present as ever. Such is the usual explanation given to account for the name, and the facts fit the theory; but the fact that several other species are called pin oaks is not accounted for. The habit of the branches of all of them is not the same. The Gambel oak in its Arizona range has that name. So has the chinquapin oak in Arkansas and Texas, but that is apparently a shortening of its true name, the last syllable only being used. They call the Durand oak pin oak in Texas, but without any known reason. The botanical name _palustris_, belonging to this species, refers to the tree’s habit of growing in swamps and damp land along river bottoms. It is not a swamp tree as cypress is, but is more like swamp white oak, and finds its most congenial surroundings on the borders of streams and on fairly well drained lowland where roots readily reach water. The leaves are three or five inches long, are simple, and alternate. They are broad, and have from five to nine lobes which are toothed, and bristle-tipped on the ends. The sinuses are broad and rounded, and extend well toward the midrib, which is stout, and from which the veins branch off conspicuously. In color the leaves are bright green above and lighter below when young, becoming thin, firm and darker green at maturity; late in autumn they turn a rich, deep scarlet. They are coated below with pubescence, and have large tufts of pale hairs in the axils of the veins. The fruit of pin oak is a small acorn which grows either sessile or on a very short stem; sometimes in clusters, and sometimes singly. In shape the acorns are nearly hemispherical, and measure about a half inch in diameter; they are enclosed only at the base, in a thin, saucer-shaped cup, dark brown, and scaly. The bark of a mature tree is dark gray or brownish-green; it is rough, being full of small furrows, and frequently cracks open and shows the reddish inner layer of bark. On small branches and young trunks, it is smoother, lighter, and more lustrous.