The third section of the family Abietinæ is formed by the genus Pinus, of which the Scots fir, or Scotch pine (Pinus sylvestris), is the type. The Abietinæ of this genus are distinguished by their foliage. There are two kinds of leaves--the primitive ones, which are little, scale-like, green up-growths closely scattered on the young branches; and the secondary ones, which are long needles carried as a tuft or fascicle on a very stumpy branchlet. These tufts of needles are persistent (that is to say, are not shed yearly), and differ from those of the larches and cedars in consisting of but few needles in a tuft, the number being characteristic of different species, some having five, others three, others two, and the American Pinus monophylla having only one. The general shape of these trees is not tapering like the spruce with unforked trunk, but they usually shed the lower branches as growth goes on, and present in most cases a trunk carrying an umbrella-like expanse of foliage-bearing branches, or several such expanses. The scales which form the cones in the genus Pinus are (with few exceptions, such as the Weymouth pine) not flat and flexible, but are thickened, swollen, and even knob-like and wooden at the exposed part, which is armed with a weak or a strong prickle (see Figs. 39, 40, and 41). The cones do not ripen until the end of the second or third season; they may be, according to species, erect, pendulous, or horizontal, and vary in size in different species. In some they remain closed on the trees for an indefinite period (even fifteen or twenty years), until opened by the heat of a forest fire or of an exceptionally hot season.
The Scots fir, Pinus sylvestris (Fig. 31), called _Pin de Genève_ by the French, has a very wide range. It extends eastward and northward from the Sierra Nevada, in Spain, through Europe and Russian Asia; its northern limit approaches the Arctic circle, its southern limit is formed by the great mountain chains of the Alps, Caucasus, and Altai range of Asia. The beautiful blue-green colour of its needles, the fine red-brown tint of its trunk and branches, and the graceful spread of its foliage high up on a few great, unequally-grown branches springing from its tall, bare trunk, are amongst the most picturesque features of English landscape. In the southern counties "clumps" of a dozen or score of these graceful trees are often to be seen on some isolated hilltop in the moorlands, and are associated with poetic tradition and ancient superstition. In the North of Britain they are more frequent as forest. The Scots fir is the only pine tree really native in our land. It is distinguished from several other species of Pinus by having the leaves or needles in bundles of two, and having relatively small oblong cones (2 to 3 inches long) which are borne near the ends of the branches (Fig. 31). The constituent scales of the cone are only slightly thickened, and the surface knob has no prickle. There are two of the common pine trees of the Mediterranean coast (the Riviera and elsewhere), namely, the Aleppo pine (Pinus halepensis) and the so-called Corsican or Austrian pine (Pinus Laricio), which agree in the above-given points with the Scots fir, and are, in fact, difficult to distinguish from it, except by general shape, mode of growth, and the colour of the leaves and stem. The needles of the Scots fir are 1½ to 3 inches long, those of P. halepensis 2½ to 3½ inches, and those of P. Laricio 4 to 6 inches long. The Pyrenæan or Calabrian pine is closely similar to these.