POPULUS ALBA Linnæus. Silver-leaf Poplar. (× 1/2.)
2. Populus heterophylla Linnæus. Swamp Cottonwood. Swamp Poplar. [Plate 16.] Tall trees up to 5-8 dm. in diameter; bark of old trees very thick, broken into long ridges which are separated by deep furrows, reddish-brown but generally weathered to ash-color; shoots densely woolly at first, becoming glabrous before the second season; leaves broadly-ovate with petioles 2-10 cm. long, more or less woolly on both surfaces on unfolding, becoming glabrous above and remaining woolly beneath, at least on the larger veins, rarely becoming entirely glabrous, usually cordate at the base, blunt at apex, margins rather regularly crenate-serrate; flowers in April; capsules ripening in June, about 6 mm. in diameter, on stalks 5-10 mm. long; wood same as the next species.
Distribution.—Along the Atlantic Coast from Connecticut to Florida and along the Gulf to Louisiana, and northward along the Mississippi Valley to Michigan. It is found in many parts of Indiana. In the northern counties it is found in "gumbo" soils in swamps. It is a common tree in the river swamps of the lower Wabash Valley where it reaches its greatest size. There are no records for the extreme southeastern part of the State, although it has been found in swamps in Harrison and Clark Counties and is found in many counties of Ohio.
Remarks.—The pith of the shoots of this species is orange which easily distinguishes it from all other species of the genus which have a white pith. This species in all of its range is closely associated with the common cottonwood, and millmen make no distinction in the price or qualities of the timber.
3. Populus deltoìdes Marshall. Cottonwood. Carolina Poplar. (Populus balsamifera var. virginiana (Castiglioni) Sargent). [Plate 17.] One of the largest trees of the Indiana forests; bark of very old trees very thick, broken into ridges up to 1 dm. or more in thickness, separated by deep furrows, reddish-brown, weathering to a gray; leaves hairy on both surfaces as they unfold, soon glabrous except on the margins which are more or less ciliate, broadly-deltoid, usually 7-12 cm. long, and about as wide, base more or less truncate or cordate, or somewhat wedge-shaped, with rather short acuminate tips, crenate-serrate; capsules ovate, about 6 mm. in diameter, on stalks 1-2 mm. long; wood light, soft, weak, sap wood white, heartwood small and brown; warps badly on drying.
Distribution.—Quebec to Florida and west to the Rocky Mountains. Throughout Indiana in low ground along streams, in swamps and about lakes. On account of its habit of growing only in low ground it is infrequent in the hill country of southern Indiana.
