Linnæus placed nearly all the hardy Abietineæ in the genus Pinus, and since his time botanists have disagreed exceedingly respecting the generic names of the different plants; no less than twelve different divisions of them having been published, by as many eminent botanists, since the commencement of the present century. The best, however, appears to be that of M. Richard, which was approved by De Candolle, and which has been adopted with a slight alteration in Mr. Loudon’s Arboretum Britannicum. According to this arrangement, the hardy Abietineæ are divided into five genera; viz., Pinus, the Pine, including all the resinous trees with long leaves, which grow two or more together in a sheath; Abies, the Spruce Fir, the leaves of which do not grow in a sheath, but are scattered round the branches, the leaves themselves being short, flat, and the same on both sides; Picea, the Silver Fir, the leaves of which resemble those of Abies, except that the edges curl in, and the under surface is quite different from the upper one, being marked with two white lines, one on each side the midrib; the leaves are also placed nearly in two rows, one on each side the branch; Larix, the Larch, the leaves of which are very slender and produced in tufts, but which fall off every winter; and Cedrus, the Cedar, the leaves of which resemble those of the Larch, but which do not fall off every winter. The distinctions between these genera in the leaves only are very clear, and easily remembered; and their cones differ as decidedly: those of the Pines are hard and thick at the tips of the scales, which remain on after the seed drops; those of the Spruce Firs are thin at the tips of the scales, which also remain on the cones after they have lost their seeds, and the cones are drooping, and tapering at both ends; those of the Silver Firs are erect, cylindrical, and of nearly the same diameter throughout, and the scales fall with the seeds; those of the Larch are erect, but small and conical, and the scales remain on after the seeds have fallen; and those of the Cedar are erect, oval, and with deciduous scales. To the hardy genera may now be added Araucaria, as one species of this genus (A. imbricata) has been found quite hardy in Britain.
The Cupressineæ are divided into four or five genera; viz., Thuja, the Arbor Vitæ, some of the species of which have been formed into a new genus under the name of Callitris; Cupressus, the Cypress; Taxodium, or Schubertia, the deciduous Cypress; and Juniperus, the Juniper. The only needle-leaved trees belonging to Taxineæ belong to the genus Taxus, the Yew, unless we separate from it the new genus Torryea.
§ 1. THE ABIETINEÆ.—THE PINE AND FIR TRIBE.
The plants included in this section, with the exception of the Larch, are evergreens. They are all lofty trees, with straight erect stems, and their branches growing in whorls or tiers, so as to produce a very peculiar and striking effect. The male and female catkins are on the same plant; the female one containing two seeds at the base of each scale. The pollen of the male flowers is so abundant that any one passing through a grove of these trees in May or June, might fancy it was raining brimstone. Most of the species are timber trees, producing the wood called deal; that used for the flooring and other parts of houses, being principally the wood of the Scotch Pine, and the Norway Spruce. Most of the species produce turpentine, which is the thin part of the sap which flows from the tree when a notch is cut in the trunk; the thick part of the sap when purified by boiling is the yellow resin. Tar is produced by cutting the roots and wood of pine and fir trees into pieces, and putting them into a sort of oven; when the tar runs from the charred wood, and lamp-black is made from the soot which collects on the roof of the oven. Pitch is boiled tar. Pyroligneous acid is obtained by burning the wood into charcoal in an iron cylinder, and condensing the vapour that arises from it.
THE GENUS PINUS.
Fig. 94.—Cone of the Scotch Pine (Pinus sylvestris).
This genus, according to Linnæus, was made to include all the Pines and Firs, the Cedar and the Larch; and this arrangement has been followed by the late A. B. Lambert, Esq., in his