B. pubesceae, the Downy Birch. Branches erect, covered all over with very close down ; leaves heart-shaped, ovate, taper-pointed, doubly and sharply serrated, very downy. A smaller species than the first, found in the bogs of Germany : a variety of it is called Bctula urticifolia in gardens.
B. none, the Dwarf Birch. Leaves orbicular, crenated, with strongly marked veins on the under side; catkins upright. A small bush, found in Lapland end the mountainous parts of other northern countries; it even stretches across the whole continent of Asia as far ns Unaluchka. To the people of the south this plant has no value, but to the Laplanders it affords a large part of their fuel ; and its winged fruits are reported to be the favourite food of the ptannigrsn. The place of this is occupied in America by a species called Betula gland ulosa.
Asiatic Birches.
B. 1Thojpattra., Indian Paper Birch. Leaves oblong, acute, with niarly simple serratures, somewhat heart-shaped at the base ; their stlIka, veins, and twigs hairy ; ripe catkins, erect, cylindrical, oblong ; bracts smooth, woody, two-parted, blunt, much longer than the fruit, which has narrow wings. A tree found on the Alps of Gurwal and Kumaon, where it was discovered by Dr. Wallieh, who informs us that its thin delicate bark furnishes the masses of flexible laminated matter, of which great quantities are brought down into the plains of India for lining the tubes of hookahs The Sanserit name of the substance is lloorja. (Wall. ' Plant. As. Ran,' vol. ii. p. 7.) The bark of this species is of a pale cinnamon colour. It is nearly allied to B. papyracea.
B. acuminata, the Tapering-Leaved Birch. Leaves ovate, lanceolate, somewhat simply serrated, taperpointed, smooth, dotted beneath, leafstalk/sand twigs quite smooth ; ripe catkins, very long, pendulous, cylindrical, crowded ; their rachis and the bracts, which are auricled at the base, downy. Found on many of the mountains of Nepaul, and in the great valley of that country, following the courts of ravers.
B. nitida, Shining Birch.
B. cylindrostochya, Cylindrical Spiked Birch. These two last 'species are found in Kumaon.
American Birches.
B. popuiifolia, the Poplar-Leaved or White American Birob. Catkins pendulous; branches perfectly hairless, drooping, very much covered with resinous warts ; leaves triangular, taper-pointed, doubly-toothed, on long weak stalks. This species is more an object of ornament than of utility. It rarely grows more than 20 or 25 feet high, except in very rich soils, when it is said to become somewhat taller. It is a native of the northern parts of North America, from the lower parts of New York, New Jersey, and Pennsylvania, to Canada. Michaux
says that its bark cannot. be divided into thin plates like that of the Paper-Birch or common European species. It is very like the Euro pean B. pendula, from which the characters we have assigned it are sufficient to distinguish it.
B. nigra (B. rubra, Michaux; B. lanuZosa, A. Mich.), the Red Birch. Branched covered closely with a short thick down, which they do not lose till the second year; leaves angularly rhomboidal, very deeply doubly serrated, acute, with the sails and veins of the underside of the leaf downy; stipules narrow-ovate, membranous, smooth, soon dropping off. A native of the borders of river, where it grows associated with planes, maples, and willows, in the southern provinces of the United States, delighting as much in heat, according to Michaux, as many other species do in cold, and therefore the best adapted for planting in the southern parts of Europe. It is a handsome species, growing as much as 70 feet high, and from 2 to 3 feet thick, and is remarkable for its bark not being white and shining, but brown, dotted with white, and slightly wrinkled. The limbs of the tree are large, and the branches terminate in long flexible pendulous twigs. Cask hoops are manufactured from its shoots when about an inch in diameter; and all the brooms used in the streets of Philadelphia, which are far better than those of Europe, are prepared from its tough and elastic twigs. In this country it is generally called B. angulata.
B. exeelsa (B. lutes, Mich.), the Yellow Birch. Catkins erect, short, thick, nearly sessile; branches exceedingly downy when young ; leaves rhomboidal, acute without any tapering, finely and regularly serrated, or nearly entire; on very downy stalks; stipules large and membra nous. Found chiefly in the coldest parts of North America along with the Paper-Bireh ; south of the Hudson River it becomes rare. Michaux states that it is principally in good alluvial soil that it thrives, in company with black and hemlock spruces and ashes ; its greatest height is from 60 to 70 feet, with a diameter of something more than 2 feet. It is said to be a handsome tree, with a straight trunk, often clear of branches as far as 30 or 40 feet from the ground. It is remarkable for the bright golden yellow of its bark, which shines as if it had been varnished. It is most like B. nigra, from which its thicker and more hairy catkins and simply serrated leaves distinguish it, independently of other characters.