This species ranges from the mountains of northern Durango to the volcanoes of Guatemala, or possibly farther south. It is found at all altitudes where Pines can grow except on the tropical levels of Guatemala. Its more hardy forms have been successfully grown in the milder parts of Great Britain and northern Italy. It is felled for lumber in many parts of Mexico. This sturdy Pine and its numberless variations present the most remarkable example of adaptation in the genus. The variations are mostly those associated with changes of environment--dimensions of cone and leaf and the number of leaves in the fascicle. These are so accurately correlated with altitude and exposure, and are so imperceptibly graded, that no specific segregations among them have yet been successfully established. The type-specimen figured by Lambert does not show the longest cone and leaf of this species. They are better represented by specimens which have been named P. filifolia. Such dimensions prevail in subtropical localities. At temperate altitudes these dimensions are much reduced, but here are found a longer form of cone and leaf (var. Lindleyi, Loudon) and a shorter form (var. rudis, Shaw). At still higher altitudes and up to the timber-limit the var. Hartwegii, Engelmann, with short leaves and a small nearly black cone is found. Among these varieties there is no such sharp distinction as these definitions imply. All dimensions of fruit and foliage and the various brown and black shades of the cone blend into each other through endless intergradations. A monograph of this species, by one who could devote some years to it on the superb volcanoes and in the delightful climates where this tree abounds, would be a valuable contribution to science. Plate XXV. (Cones and leaves much reduced.) Fig. 220, Cone and leaves of Lambert's plate. Figs. 221, 222, Longer cones and leaves of the species. Fig. 223, Cone and leaves of var. Lindleyi. Fig. 224, Cones and leaves of var. rudis. Fig. 225, Cone and leaves of var. Hartwegii. Fig. 226, Magnified leaf-sections. Figs. 227, 228, Two forms of the dermal tissues of the leaf, magnified. Fig. 229, Habit of the tree. [Illustration: PLATE XXV. PINUS MONTEZUMAE] 39. PINUS PONDEROSA