Resinous aromatic trees, with thin scaly bark, soft durable straight-grained heartwood, thin nearly white sapwood, slender spreading or erect branches, pyramidal heads, flattened lateral pendulous branchlets disposed in one horizontal plane, forming a flat frond-like spray and often finally deciduous, and naked buds. Leaves decussate, scale-like, acute, stomatiferous on the back, on leading shoots appressed or spreading, rounded or slightly keeled on the back, narrowed into long slender points, on lateral branchlets much compressed in the lateral ranks, prominently keeled and nearly covering those of the other ranks; on seedling plants linear-lanceolate, acuminate, spreading or reflexed. Flowers minute, monœcious, from buds formed the previous autumn, terminal, solitary, the two sexes usually on different branchlets; male ovoid, with 4—6 decussate filaments, enlarged into suborbicular peltate connectives bearing on their inner face 2—4 subglobose anther-cells; female oblong, with 8—12 oblong acute scales opposite in pairs, the ovuliferous scales at their base bearing usually 2 erect bottle-shaped ovules. Fruit an ovoid-oblong erect pale cinnamon-brown cone maturing in one season, its scales thin (thick in one species), leathery, oblong, acute, marked near the apex by the thickened free border of the enlarged flower-scales, those of the 2 or 3 middle ranks largest and fertile. Seeds usually 2, erect on the base of the scale, ovoid, acute, compressed, light chestnut-brown; seed-coat membranaceous, produced except in one species into broad lateral wings distinct at the apex; cotyledons 2, longer than the superior radicle.
Thuja is confined to northeastern and northwestern America, to Japan, Korea and northern China. Five species are recognized. Of the exotic species the Chinese Thuja orientalis, L., with many varieties produced by cultivation, is frequently planted in the United States, especially in the south and west, for the decoration of gardens, and is distinguished from the other species by the thick umbonate scales of the cone, only the 4 lower scales being fertile, and by the thick rounded dark red-purple seeds without wings.
Thuja is the classical name of some coniferous tree.
CONSPECTUS OF THE NORTH AMERICAN SPECIES.
Fruit with usually 4 fertile scales.1. [T. occidentalis] (A). Fruit with usually 6 fertile scales.2. [T. plicata] (B, F, G).
1. [Thuja occidentalis] L. White Cedar. Arbor-vitæ.
Leaves on leading shoots often nearly ¼′ long, long-pointed and usually conspicuously glandular, on lateral branchlets much flattened, rounded and apiculate at apex, without glands or obscurely glandular-pitted, about ⅛′ long. Flowers opening in April and May, liver color. Fruit ripening and discharging its seeds in the early autumn, ⅓′—½′ long; seeds ⅛′ long, the thin wings as wide as the body.
A tree, 50°—60° high, with a short often lobed and buttressed trunk, occasionally 6° although usually not more than 2°—3° in diameter, often divided into 2 or 3 stout secondary stems, short horizontal branches soon turning upward and forming a narrow compact pyramidal head, light yellow-green branchlets paler on the lower surface than on the upper, changing with the death of the leaves during their second season to light cinnamon-red, growing darker the following year, gradually becoming terete and abruptly enlarged at the base and finally covered with smooth lustrous dark orange-brown bark, and marked by conspicuous scars left by the falling of the short pendulous lateral branchlets. Bark ¼′—⅓′ thick, light red-brown often tinged with orange color and broken by shallow fissures into narrow flat connected ridges separating into elongated more or less persistent scales. Wood light, soft, brittle, very coarse-grained, durable, fragrant, pale yellow-brown; largely used in Canada and the northern states for fence-posts, rails, railway-ties, and shingles. Fluid extracts and tinctures made from the young branchlets are sometimes used in medicine.
Distribution. Frequently forming nearly impenetrable forests on swampy ground or often occupying the rocky banks of streams, from Nova Scotia and New Brunswick, northwestward to the mouth of the Saskatchewan, and southward through eastern Canada to southern New Hampshire, central Massachusetts, New York, central Ohio, northern Indiana and Illinois, and Minnesota; occasionally on the high mountains of Virginia, West Virginia, and northeastern Tennessee, and on the mountains of western Burke County, North Carolina, at an altitude of 3000 feet; very common at the north, less abundant and of smaller size southward.