- [Footnote: of which 165 belong to the northern and 51 to the
southern hemisphere. Since my researches these proportionate numbers must be modified, as, including the species of Pinus, Cupressus, Ephedra, and Podocarpus, found by Bonpland and myself in the tropical parts of Peru, Quito, New Granada, and Mexico, the number of species between the tropics rises to 42. The most recent and excellent work of Endlicher, Synopsis Coniferarum, 1847, contains 312 species now living, and 178 fossil species found in the coal measures, the bunter-sandstone, the keuper, and the Jurassic formations. The vegetation of the ancient world offers to us more particularly forms which, by their simultaneous affinity with several different families of the present vegetable world, remind us that many intermediate links have perished. Coniferæ abounded in the ancient world: their remains, belonging to an early epoch, are found especially in association with Palms and Cycadeæ; but in the latest beds of lignite we also find pines and firs associated as now with Cupuliferæ, maples, and poplars. (Kosmos, Bd. i. S. 295-298, and 468-470; Engl. edit. p. 271-274, and lxxxix.)
If the earth's surface did not rise to considerable elevations within the tropics, the highly characteristic form of needle-leaved trees would be almost unknown to the inhabitants of the equatorial zone. In common with Bonpland I have laboured much in the determination of the exact lower and upper limits of the region of Coniferæ and of oaks in the Mexican highlands. The heights at which both begin to grow (los Pinales y Encinales, Pineta et Querceta)]*
