The name cedar is applied to a variety of trees, including species of several genera of Conifers, Juniperus, Thuja, Libocedrus and Cupressus.
Thuja gigantea of western North America is known in the United States as White (or Yellow) cedar, and the same name is applied to Cupressus Lawsoniana, the Port Orford or Oregon cedar, a native of the north-west States, and one of the most valuable juniper trees of North America.
Pines of three species, junipers, larches, oaks, maples, willows and the Thuja Orientalis have been identified.
Among the indigenous trees are the Abies excelsa, Abies microsperma, Pinus sinensis, Pinus pinea, three species of oak, five of maple, lime, birch, juniper, mountain ash, walnut, Spanish chestnut, hazel, willow, hornbeam, hawthorn, plum, pear, peach, Rhus vernicifera, (?) Rhus semipinnata, Acanthopanax ricinifolia, Zelkawa, Thuja orientalis, Elaeagnus, Sophora Japonica, &c. Azaleas and rhododendrons are widely distributed, as well as other flowering shrubs and creepers, Ampelopsis Veitchii being universal.
The name Thuja, which was adopted by Linnaeus from the Thuya of Tournefort, seems to be derived from the Greek word Obos, signifying sacrifice, probably because the resin procured from the plant was used as incense.
Thuja occidentalis is the Western or American arbor vitae, the Cupressus Arbor Vitae of old authors.
The wood is very durable and useful for outdoor work, such as fencing, posts, etc. Another species of arbor vitae is Thuja orientalis, known also as Biota orientalis.
Thuja gigantea, the red or canoe cedar, a native of north-western America from southern Alaska to north California, is the finest species, the trunk rising from a massive base to the height of 150 to 200 ft.
The name Retinospora, therefore, does not stand for a true genus, but denotes persistent young forms of Juniperus, Thuja, Cupressus, &c., in which the small scaly leaves of ordinary species are replaced by the slender, needle-like leaves, which stand out more or less at right angles from the branches.
The flat branchlets of Cupressus, Thuja (arbor vitae), Thujopsis dolabrata (Japanese arbor vitae) are characteristic of certain types of conifers; in some cases the horizontal extension of the branches induces a dorsiventral structure.
Sequoia sempervirens (redwood), Thuja occidentalis, &c. The leaves of conifers are characterized by their small size, e.g.
The needle-form represented by Pinus, Cedrus, Larix, &c., the linear flat or angular leaves, appressed to the branches, of Thuja, Cupressus, Libocedrus, &c. The flat and comparatively broad leaves of Araucaria imbricata, A.
In the North American area Picea alba, P. nigra, Larix americana, Abies balsamea (balsam fir), Thuja canadensis (hemlock spruce), Pinus Strobus (Weymouth pine), Thuja occidentalis (white cedar), Taxus canadensis are characteristic species.