Fig. 99.—Young plant of the Arbor Vitæ.
There are several species of this genus, but only two are common in British gardens. Of these the American Arbor Vitæ (Thuja occidentalis) is the largest tree; though it seldom grows above 30 feet high, and it is a great many years before it even attains that height. The male flowers and the female flowers are distinct, but on the same tree. The male catkins are small cones, with the pollen inclosed in four cases that are attached to the inside of the scale, near its base. The female catkins consist of six scales, with two ovules at the base of each; and the ripe cone has a sharp point projecting from each scale. The seeds have scarcely any wing; and when they germinate, they have only two cotyledons. The young plants send down a very long tap root (see fig. 99), and have some of their leaves imbricated and others loose. The Chinese Arbor Vitæ (T. orientalis) seldom reaches the height of 20 feet, but it may be also distinguished from the preceding species by its more dense habit of growth, by its branches being turned upwards instead of spreading horizontally, and by its leaves being smaller, closer together, and of a lighter green.
THE GENUS CALLITRIS.
Callitris is a genus separated from Thuja, of which only one species is as yet common in British shrubberies. This is the Gum Sandarach-tree, formerly called Thuja articulata, but now named Callitris quadrivalvis. The branches of this tree are articulated, that is, they may be broken off at the joints without lacerating the bark. The leaves are very small, quite flat, and articulated like the branches. The male catkins form a cone, in which the scales are disposed in four rows, with three or four anthers at the base of each. The female catkins are solitary, and they divide, when ripe, into four woody valves or scales, only two of which bear seeds. The seeds are small, and have a wing on one side. The tree is a native of Morocco and Barbary, in which countries it produces the gum-sandarach, which exudes like tears from every part of the plant. The wood is fragrant, very finely grained, and extremely durable, as is shown in the roof of the Cathedral of Cordova, built in the ninth century, which is of the wood of this tree.
THE GENUS CUPRESSUS.—THE CYPRESS.
The evergreen cypress (Cupressus sempervirens) is a cone-like, tapering tree, with its branches growing close to its trunk, and rarely attaining the height of fifty feet even in its native country. The male catkins are longer than those of the arbor vitæ, and the female ones contain more ovules. The cone is buckler-shaped, and it divides, when ripe, into eight or ten corky scales, each of which has four nuts attached; the cone being partially divided into cells, which may be seen, when the scales have been removed to show the interior. The pollen of each male flower is contained in four cells, attached to the lower part of the inside of the scales. The wood is remarkably hard and fragrant, and it is of a fine close grain; it is also very durable. It is supposed to have been the gopher-wood of Holy Writ, and the citron-wood of the ancient Romans, the beauty of which in tables was so celebrated.
The White Cedar (Cupressus thyoides) is a species of Cypress, having imbricated leaves, and the same kind of cone; and the Cedar of Goa (C. lusitanica) is another species of Cupressus, which appears from the shape of its cones to be nearly allied to the Arbor vitæ. There are some other species, but they are not common in British gardens.
THE GEXUS TAXODIUM.—THE DECIDUOUS CYPRESS.
The Deciduous Cypress (Taxodium distichum) has numerous leaves arranged in two even rows, one on each side of the branch, which fall off in autumn, assuming a reddish tinge before they drop. This genus was separated from Cupressus, because the male catkins, instead of being produced singly at the tips of the branches, are in clusters or panicles, and the anther-like scales, have the pollen in five cells. The cone, which is very small, has only two seeds to each scale, instead of four; and the young plant has five or more cotyledons, while the Cypress has only two. The deciduous Cypress was placed in the genus Cupressus by Linnæus, and afterwards it was called Schubertia disticha by Mirbel. The tree, which grows 120 feet high and upwards in America, with a trunk forty feet in circumference at the base, has generally, when of this size, the lower part of its trunk hollow, often to the height of five feet or six feet from the ground. The roots also send up conical protuberances two feet high, and four feet or five feet wide, which are always hollow. These curious knobs are called in America “cypress knees;” and the negroes use them for bee-hives. The wood of the deciduous Cypress is used in building in Virginia. There is another species (T. sempervirens) which does not lose its leaves in winter, a native of California, but it has not yet been introduced.