Abies (Fir). The leaves are often (e.g. Ab. pectinata) displaced into 2 rows, flat and indented at the apex, with 2 white (wax-covered) lines on the under surface, in which the stomata are situated. The leaf-scars are nearly circular and do not project. The cones are erect. The cover-scales and the ovuliferous scales separate from the axis, to which they remain attached in other genera.—Tsuga has leaves like Abies, but by the slightly projecting leaf-scars, and cones with persistent scales, it forms the transition to Picea.—Pseudotsuga has leaves similar to those of Abies and persistent carpels as in Picea, but the cover-scales grow as in Abies and project beyond the ovuliferous scales (P. douglasii, Fig. [267]). These two genera are considered as sub-genera of Abies.—Picea. The leaves project on all sides, square and pointed; the leaf-scars are rhombic, on projecting leaf-cushions. The cones are pendulous. The cover-scales are much shorter than the leathery, persisting ovuliferous scales.—The genus Larix (Larch) differs from all the others in having deciduous leaves (the three preceding have leaves which persist for eleven to twelve years). It has long-branches with linear foliage-leaves and short, thick, perennial dwarf-branches, which each year form a new rosette of foliage-leaves, similar to those on the long-branches. The male flowers and the erect cones resemble those of Picea, and are borne on dwarf-branches.—Cedrus (Cedar) resembles Larix to some extent, but has persistent leaves (C. libani, C. deodara).—Pinus (Pine) has long-branches and dwarf-branches. The leaves of the long-branches are scale-like and not green; the dwarf-branches have very limited growth, and persist for three years; they arise in the axils of the scales borne on the long-branches of the self-same year, and each bears 2–5 foliage-leaves, they are also surrounded at the base by a number of membranous bud-scales. The cone-scales have a thick, rhomboid extremity (the “shield”).
The buds which develope into long-branches arise at the apex of other long-branches, and being very close together, form false whorls. The female cones occupy the position of long-branches, and take about two years for their development. The male flowers arise close together, and form a spike-like inflorescence at the base of a long-branch of the same year. The male flowers occupy the position of dwarf-branches, so that a female cone may be considered to be a modified long-branch, and a male cone a modified dwarf-branch. The main axis of the seedling has needle-like leaves, similar to those found on the older parts, and on dwarf-branches; it is not until some time later that the dwarf-branches are developed and the permanent arrangement attained.
Uses. Several species are commonly cultivated in this country, partly on heaths and moors, and partly in plantations and as ornamental trees, such as Mountain Pine (Pinus montana, Cen. Eur.); Austrian Pine (P. laricio, Eur.); Scotch Fir (P. silvestris, Eur.); Weymouth Pine (P. strobus, N. Am.); common Red Pine (Picea excelsa, Cen. and N. Eur.); White Pine (P. alba, N. Am.); Abies pectinata (Common Fir, S. and Cen. Eur); A. nordmanniana (Crimea, Caucasus); A. balsamea (N. Am.); Tsuga canadensis (N. Am.); Pseudotsuga douglasii (N.W. Am.); Larch (Larix europæa, Alps, Carpathians); L. sibirica (N.E. Russia, Siberia).—The wood of many species, especially Pine, on account of its lightness and because it is so easily worked, is very well adapted for many useful purposes. The wood of the Yew-tree is very hard and is used for ornamental turning. Resin and Turpentine (i.e. Resin with essential oils, the name being derived from the Terebinth-tree, from which formerly a similar material was obtained) are extracted from Pinus laricio and P. pinaster. Oil of Turpentine is obtained by distillation of turpentine with water; Tar by dry distillation of Pine-wood. Canada-balsam is from North American Abies-species (A. balsamea and Fraseri). The officinal Turpentine is mainly obtained from Pinus pinaster (South of France), P. tæda, australis, strobus (Weymouth Pine) and other North American species; more recently also from P. silvestris (Scotch Fir), maritima, laricio, Picea excelsa, and others; Venetian Turpentine, from Larch (S. Eur.) Amber is resin from a Tertiary plant (Pityoxylon succiniferum), closely related to the Pine, which grew especially in the countries round the South-East coast of the Baltic. Pinus pinea (the Pine, S. Eur.) has edible seeds and also P. cembra (in Cen. Eur. and Siberia).
Order 3. Taxodiaceæ. The vegetative leaves and cone-scales are arranged spirally. The ovules (2–9) are situated either at the base of the ovuliferous scales, in which case they are erect; or at their centre, when they are generally more or less inverted. The ovuliferous scale is more or less united with the cover-scale, and projects beyond the surface of the cone-scale, like a comb (Fig. [269]). The vascular bundles, which extend into the cover-scale, have the usual leaf-arrangement, viz. the wood placed above the bast; while those bundles which enter the ovuliferous scale have this arrangement of the bundles reversed.
Fig. 269.—Cryptomeria japonica. Portion of longitudinal section through female flower. d cover-scale; f ovuliferous scale; ov ovules; fv and fv’ vascular bundles; the xylem is indicated by a wavy line, and the phlœm by a straight line.
Taxodium distichum (the North American “Swamp Cypress”) has annual dwarf-branches, with distichous leaves, and cone-like “pneumathodia.” In the Tertiary period it was very common in the Polar regions. Sequoia (Wellingtonia) gigantea is the famous Californian Giant-Fir, or Mammoth-Tree, which attains a height of 300 feet, a diameter of 36 feet, and is said to live for 1,500 years. Cryptomeria japonica (Japan, China) has the least adnate ovuliferous scales; Glyptostrobus (China); Arthrotaxis (Tasmania); Sciadopitys verticillata (the only species in Japan) has, like Pinus, scale-like leaves on the long-branches, of which those which are situated at the apex of the annual shoots support “double needles,” i.e. dwarf-branches similar to the two-leaved dwarf-branches in Pinus, but without bud-scales, and with the two leaves fused together at the edges into one needle, which turns its upper surface away from the long-branch.
Order 4. Cupressaceæ (Cypresses). The leaves are opposite or verticillate, sometimes acicular, but most frequently scale-like (Fig. [270]). In the species with scale-like leaves, the seedlings often commence with acicular leaves (Fig. [272]), and branches are sometimes found on the older plants which revert to this form, seeming to indicate that the acicular leaf was the original form (atavism). The so-called “Retinospora” species are seedling-forms of Biota, Thuja, Chamæcyparis, which have been propagated by cuttings, and retain the seedling-form. The flowers are monœcious or diœcious. The male flowers are short, and have shield-like stamens, bearing most frequently several pollen-sacs. The cover-scales and ovuliferous scales are entirely fused together and form undivided cone-scales, opposite or whorled; the ovuliferous scales have slight projections near the base on which 1–2–several erect ovules are developed (Fig. [274]). Most frequently 2 cotyledons.—Evergreen trees and shrubs.
Fig. 270.—Cupressus goveniana.