Zones of the Central and
Southern   Parts  of   North

Mixed and deciduous forests are found south of the coniferous fo­rests. They do not cut across the continent from west to east, but grow in the western part only where the climate is wetter. From there they spread south, almost reaching the Gulf of Mexico.
Compared with the deciduous forests of Europe, those of North America are more varied. This is especially noticeable in autumn, when the leaves are bright and many-coloured. The chief trees are
the mixed and deciduous forests have been felled, and hardly any measures are taken to replant them.
Prairies. West of the mixed and deciduous forests the climate becomes drier, and instead of forests there is chiefly grass. The steppes of North America are called prairies. They are covered with tall, thick grass, including feather-grass and others. Closer to the Cordille­ras the rainfall is still lower and the vegetation poorer. Here and there grow tufts of low grass.

Fig. 161. Cacti on the Mexican Upland.

Before the coming of the Europeans great herds of bison used to roam over the plains (a bison is a large kind of wild ox, something like the European aurochs). They were hunted by the Indians, and now only a few are left in reserves and zoos. The first white settlers brought horses with them, and herds of mustangs (wild horses) were soon galloping over the prairies.
Today the prairies are almost entirely under cultivation. The only animals that are more or less plentiful are small rodents.
The soil is very fertile. Much wheat and corn is grown.
On the capitalist farms great areas are often planted with the same crops many years running. In the race for profits little thought

Fig. 160. Bisons.

is given to the effect on the soil. Exhausted and loose, it is easily washed away by the rain, and ravines are formed. The surface soil turns into fine dust, especially in the arid regions. Particles are raised by the wind, and in dry weather day cannot be distinguished from night. Large districts suffer from such storms. Thus, vast areas are gradually becoming barren and unfit for farming (bad lands).
Deserts and Semideserts. The plateaus between the Cordillera ranges are desert and semidesert regions. In California they extend to the very Pacific. Only wormwood and prickly scrubs grow there.
Peculiar to Mexico are the cactus and agave. These plants are adapted to the dry climate. They have thorns or spines instead of leaves, and their green, fleshy stems are stores of moisture. There are many kinds of cactus that differ in shape. Some have tall, branchy stalks; others are ball-shaped and grow close to the ground; still others have broad flat leaves that grow one from the other. Side by side with cacti grow agaves. These consist of bunches of fleshy, sap-laden leaves on tall stalks. For a number of years they seem to be collecting the strength needed to send forth the tree-like stalks and produce flowers and seeds. Immediately after they wither.
The semideserts and deserts are thinly inhabited. The chief occu­pations are sheep-breeding and mining.
Subtropical and Tropical Regions. In the Gulf of Mexico coast-lands and in Florida the vegetation is of the wet tropical type. In Florida grow evergreen trees entwined with climbers. In the dry subtropical regions on the Pacific coast north of California the vegetation is much poorer. On the watered lands, however, oranges, lemons, apples and grapes are grown.
In the West Indies and in Central America there are tropical forests and savannahs. Man has greatly changed the face of nature in the tropical regions of North America. There are many plantations on which southern fruits, bananas and sugar-cane are grown. The native population is ruthlessly exploited by the United States capi­talists who own the plantations.