3. _The Mountain region, or region of deciduous trees._--Many writers take the growth of corn as the characteristic of the colder temperate zone, corresponding to what has been called the mountain region of the Alps. But so many varieties, all with different requirements, are in cultivation, that it is impossible to take the growth of cereals in general as marking clearly any natural division of the surface. A more natural limit is marked by the presence of deciduous trees (trees which shed their leaves). Although the oak, beech, and ash do not exactly reach the same height, and are not often seen growing side by side in the Alps, yet their upper limit marks pretty accurately the transition from a temperate to a colder climate that is shown by a general change in the wild, herbaceous vegetation. The lower limit of this zone is too irregular to be exactly defined, but its upper boundary is about 4,000 feet on the cold north side of the Alps, and often rises to 5,500 feet on the southern slopes, which of course get more sunshine and warmth. The climate of this region is favourable to the growth of such trees as the oak, beech, and ash, but it does not follow that we should see them there in any great numbers at the present time; for it is probable that at a very early date they were extensively destroyed for building purposes, and to clear space for meadow and pasture land, so that with the exception of the beech forests of the Austrian Alps, there is scarcely a considerable wood of deciduous trees to be seen anywhere in the chain. In many districts where the population is not too dense, the pine and Scotch fir have taken the place of the oak and beech, mainly because the young plants are not so eagerly attacked by goats, the great destroyers of trees.