Page:Popular Science Monthly Volume 34.djvu/244

232, we pass through, regions occupied by like series of vegetation. Pursuing our course from north to south, we find the beech giving place in lower latitudes to varieties of oak; and it is one of the effects of this movement that other oaks appear at first in scattered colonies, as does also the chestnut, which, aside from its requirements as to the composition of the soil, seems to find, especially in southern Europe, the conditions normal to its forest development. The association of foliage-trees, whose outline is thus sketched, which would cover central Europe with a continuous forest if the continent had not been taken possession of by cultivation, is found on the southern slopes of the great mountain-ranges, only under specially favorable conditions of altitude and moisture. Its principal characteristics, besides the particular grouping of species, result from the winter caducity of the leaves, to the law of which the holly, the box, and the ivy—types also belonging to the next southern or Mediterranean group—are almost the only exceptions.

The Mediterranean group touches abruptly on the preceding one, and derives its name from the Mediterranean Sea, of which it occupies the whole periphery. In all the regions within this perimeter a similar forest flora covers with the same species a soil generally hilly, under a climate dry and warm, while subject to violent contrasts. The evergreen oaks, other oaks with semi-persistent foliage, the laurel, olive, pomegranate, terebinths, some of the maples, the oleander, and the carob; numerous shrubs with persistent leaves—laurestinuses, arbutuses, mock-privets, daphnes, heaths, cistuses, etc.—contribute to the constitution of this assemblage, which is all the more striking because an astonishing richness of characteristic details is concealed in it under an apparent uniformity. A more careful examination of the elements of which this flora is composed is demanded if we undertake to seek their origin. Besides the foliage-trees, the group includes conifers which are peculiar to it. The pines alone cover a large extent, one of them, the Aleppo pine, being very generally diffused, while a number of other species have each their determined station and place. The mountains in the interior of the region bear species that are special to them, and it is to such scattered islands of vegetation that we are indebted for such choice garden-plants as the spruces of Andalusia, Numidia, Mount Parnassus, Cephalonia, and Cilicia. In the same category are the cedars, which, with different names and varietal distinctions, people the ridges above a certain level of altitude of the Taurus, Lebanon, and Atlas. These are the mountaineer conifers, adapted to the Alpine stations of the Mediterranean region, where the altitude permits the beech, chestnut, maples, lindens, and birch to reappear and maintain themselves here and there in sporadic colonies.