The word "pine" is of Latin origin, and belongs properly to the South of Europe; the word "fir" is Teutonic, and is originally applied to the same trees in the North of Europe as those to which "pine" is applied in the South. It is of no use trying to determine what conifers should rightly be called "firs" or "fir trees," and which "pines" or "pine trees." There is complete confusion and indifference nowadays in the use of those words, and the botanists have in the past added to the confusion by their changing and uncertain use of the names Pinus and Abies. A definite system of naming has now been agreed upon, and we must, in order to understand one another in talking about conifers, strictly accept and adhere to the names at this moment assigned to them by the common consent of botanical authorities. [Illustration: FIG. 31.--A fertile branch of the Scots Fir, Pinus sylvestris, showing the small male cones, _m.c._, and the larger female cones, _f.c._, also the foliage needles grouped in pairs. Drawn of two-thirds the natural size, linear. The lower figures relate to the male cone. a, A ripe male cone, slightly enlarged; b, inner face of one of the scales of the male cone, showing the paired pollen-producing or stamen-like patches--much magnified; c, outer face of the same scale.] The Scots fir is Pinus sylvestris. "Pinus" is the name of a genus of conifers, and includes many species besides sylvestris, our own familiar Scots fir, which is often now spoken of by the queer, ill-sounding title of Scotch pine. The Norway spruce or pine, called often "common spruce," also "the spruce fir," and "Christmas tree," is the "Picea excelsa" of correct botany. There are several other species of the genus Picea. A third well-known conifer, the silver fir, is called by botanists "Abies pectinata"; there are many other species of Abies. Although it has such a familiar, sweet-sounding name, the silver fir is not a common tree in England, where it was introduced only three hundred years ago. It will not thrive at Kew Gardens. It is the common forest-making fir of the centre of France and of much of the mountainous country of Southern Europe,[14] but it is rarely to be seen in the Swiss mountains (only in certain relatively low-lying valleys). The pine forests of those mountains are almost exclusively formed by the spruce, with the addition of a few Scots firs and larches, and in some parts of the Arolla fir or pine. [14] It is, according to botanical authorities, from the wood of the silver fir, which still grows on Mount Ida, that the Greeks, as related by Virgil, constructed the Trojan horse. "Instar montis equum, divina Palladis arte Ædificant, sectaque intexunt _abiete_ costas! (A horse of mountain size they build By art divine of Pallas helped And weave its ribs with planks of fir). "Æneid," ii. 15.