Modern Geography

ion of hills and valleys which is due to the joint action of atmospheric agents, running water and ice, and considered briefly some

ductive by ice, by lava, by a total lack of water, or by the existence of poisonous salts, it is clo

trees for long generations before he got back to the forest and to the grassland as they occur in nature. Plants as individuals are the province of the bo

cs and in temperate zones, we find that plants reach their maximum size, combined with great differentiation of structure, and the formation of woody stems which offer

the Congo forest, and the negritos of the Philippines, and he suffers from a chronic insufficiency of food, which acts as a check both to his mental and physical development. There has, therefore, always been war between evolving man and the giants of the p

the grasslands. The grasslands favour man in several respects. They feed the animals upon which he depends for food, for clothing, and for the conveyance of his person or property, and they offer much less resistance than the forest to his agricultural operations. Even the large herbivorous mammals which in their wi

up the struggle, and diminish in number, losing their power of forming a complete covering for the soil, and thus the gr

grasslands are for ever attempting to encroach upon the woodlands, and in this attempt they have been assisted, sometimes to too great an extent, by the operations of man. Similarly the desert is a

y the amount and distribution of precipitation, by the nature and strength of the winds, by the characters of the soil, and so on. But forests occur under the equator and also far to the north; we have cold deserts as well as hot

soils. We are thus led to the conclusion that it is the precipitation and the wind which determine the distribution

be weak, or it has a poisonous effect. For example, sulphate of ammonia is a valuable manure, but if a consider

of surplus water, the process being called transpiration. Transpiration takes place faster in a tall plant like a tree, which grows up into dry layers of the air, than in a low plant like a grass. It takes place faster in windy weather t

son 354 tons of water per acre, which illustrates the drying effect of the presence of the wood. Similarly, the effect of tree-planting in the marshy regions of France and Ital

the water, and these pass deep down into the soil, and spread out over a vast area. In other words, trees avail themselves of the water in the deeper layers of the soil, and can tolerate relatively

g this season. On the other hand, drying winds are very hurtful to trees, especially if they occur at a period when the tree is unable, either because of the coldness of the subsoil, or because of its dryness, to take in fres

depend upon the water in the upper layers of soil, and must have frequent, even if gentle, showers during their

ibe later, and this scrub passes in all directions into desert land. Here no belt of grassland intervenes, for the rainless Mediterranean summer makes the growth of grass virtually impossible, except where special conditions, e. g. hills, introduce modifications. Contrasted with this we have the conditions in North America where, e. g. in Canada, the western coast is densely forest-clad, as is also the eastern region. In journeying

Sahara desert, but to the south of the desert the grassy and park-like Sudan separates the desert from the luxu

mperature variations, which is the dominating factor. Moisture is usually abundant, but high up what is called phys

which occur in a group than on isolated peaks. As the wind is more and more felt, and increases the dangerous transpiration of winter the trees become more and more dwarfed to escape its force. There may be a belt of prostrate mountain pines above, marking the tree limit; in any case the trees are gradually replaced by dwarfed shrubs. Then comes the zone of Alpine plants,

es in the Alps induced man to destroy the forest in order to increase pasture land. The result has often been disastrous, for once the trees are cut down the forest soil is rapidly destroyed by weathering, especially on slopes, the courses of streams are alte

habitants of more northern climates in spring gives rise to a somewhat erroneous impression in regard to the plants. In spring the Mediterranean vegetation is at its best. The mild winters permit the plants which further north die down or cease to grow, to go on

trive to flower and fruit before the forest trees are thickly clad with leaves. The snowdrop, even the wild hyacinth, though it is much later, simi

h narcissus, asphodel, bell hyacinth, Allium, tulips, and so on, all awakened by the spring warmth and the spring rains. Accompanying them are many bright-coloured annuals, also in a hurry to race through their life-history before the terrible drought of summer. Now also the grass grows, and the autumn-sown corn becomes

n by arranging themselves with the edge upwards instead of the flat surface, makes them appear smaller than they are. They are often needle-shaped, sometimes shining and coated with resin, sometimes silvery owing to a coating of hairs on the under surface. Many plants have spines or thorns, and succulent plants like agave, aloe and prickly pear are common. The absence of a

ripening fruit. The gorgeous scarlet flowers of the double pomegranate gleam amid the dark foliage; the gnarled and twisted olives show on close inspection masses of small g

takes advantage of the rapid growth of annuals in the early part of the year. The annuals most useful to him, here as elsewhere, are, of course, the cereals, especially

ding artificial supplies of water. The most important of these, throughout the whole Mediterranean area, are the vine and the olive. The olive supplies the oil which is all the more necessary in that the absence of grass makes pastor

the evergreen oak is a true oak. Both trees, however, show similar adaptations to summer drought, and their resemblance to one another is a good example of convergence due to a similar environment. Both have small evergreen leaves; small that they may not lose too much water in summer, evergreen that they may assimilate even during the winter. Both hav

ee later, but the point of interest is that the plants which have been of importance in the history of the region

the long ages he has inhabited the Mediterranean, man has doubtless contributed largely to the destruction of the forests which are now, as we have seen, represented by the stunt

ded head, is very characteristic. We have already mentioned the evergreen or holm oak as common, and the cork oak occurs abundantly in some places. These trees, with the cypress, must have formed the primitive forests, and they still constitute the most important

f resin on their leaves. This, no doubt, preserves them against loss of water, but also probably protects against grazing animals. Goats thrive in the Mediterranean partly because of the catholicity of their taste in vegetation, and in consequence the plants have had to protect themselves against their appetite as well as aga

r, the noble laurel, the tree heath, arbutus, many kinds of broom,

een, the forest which once covered most of the area, except the steppe region of southern Russia, has

thing but their branches to the winter blasts. While the buds of Mediterranean plants have no special means of protection, the typical forest trees of Central Europe have their buds carefully sheathed in scales, clothed in hairs, or coated with resin, to keep out alike the

dominant species, forming beech woods or oak woods, and so on. The dense shade of the beech makes undergrowth difficult or impossible, but the other woods have a complicated undergrowth of many different kinds

ers, with the exception of the larch, are evergreen, and all are more tolerant of cold and wind than deciduous trees. Pines, spruce, fir, larch, and silver fir are the most imp

, with small leaves and other adaptations to ensure against excessive loss of water. It is, as it were, the reappearance of the Mediterranean type, but here the cause is, not the absence of water, but the f

re the presence of peat produces conditions very unfavourable to plant life, except to certain shrubby plants such as heather and other plants of the heather family, juniper, bog myrtle, and so on, and some grasses a

regions, are infrequent in Europe. They occur in Southern Russia and in the Hungarian plain, and form part

a period of drought. The scanty rains come in early summer, which suits grasses admirably, while the total precipitation is too slight for trees. The summers are hot, and the ra

egions well suited to the pastoral industries, which tend

and in those great peninsulas and islands which are bathed by it, a zone of modified woodland passing into scrub, remarkable for the rapid growth of annuals in the early part of the year, and for the abundance of trees bearing useful fruits. Finally, linking Europe to temperate Asia, we have belts of steppe land, characterised by a luxu

e size of the continent, offers more re

tern uplands enclosing between them a region of moderate relief-and also what has been said in regard to its climates a

band of predominantly coniferous forest, which, although its species are different, yet in broad outline is entirely homologous with the coniferous forest found in northern Asia, south of the tundra region. In C

nd gardens within recent years, and although it is perhaps the great Sequoia (Wellingtonia) gigantea which has most impressed popular imagination, it must be remembered that size and luxuriance are characteristic of many species. This western forest stretches down the western seaboard to the State of California, and, indeed, persists until increasing aridity makes forest growth impossible. Its great luxuriance, compared with the scantier forests of the Mediterranean region in Europe, is partly to be ascribed to a greater rainfall, and doubtless partly to man's inte

ain range, a dry and semi-desert region occurs, between the two, which bears a desert type of vegetation, including especially a plant related to our wormwood, called sagebrush, with cactuses in the warmer parts. Another area which is too arid to carry trees, except where local conditions raise the rainfall,

Southward the Great Plains pass into the deserts of Mexico, but northwards they are separated from the northern coniferous forest by a belt of aspen, a

ough about 25 degrees of latitude, should be uniform throughout. In point of fact, botanists distinguish three separate zones. In south-eastern Canada and the New England states the Weymouth pine (Pinus strobus) predominates, being accompanied by limes, ashes, maples, oaks, elms, chestnuts, and so forth. Further south, and especially further west, extending to the Mississippi plains, there is a deciduous forest extraordinarily rich in species. Practically all our common genera of fore

even in the warmer parts of the west coast. The reason is probably the same as in the Mediterranean region in Europe. The existence of a belt of desert to the south of the present "Mediterranean" region of western America made it difficult for the trees to mig

mmer maximum, and the temperature is high. There is thus no need to economise water, and where the soil permits there is a luxuriant type of forest, which recalls that of the tropics, although it is p

vely few species, (2) mixed coniferous and deciduous forest with chiefly the harder types of deciduous trees, (3) predominantly deciduous forest with many of the lar

o California, though it is richer, and more luxuriant in the warmer regions when moisture is still obta