124 PHYSICAL GEOGRAPHY.

 

times of the year, or is abundant during the sea-
son the tree is growing, as in the zones of the
variable winds. Forests may also occur in por-
tions of the tropics where moisture is abundant.

The forests of the cold temperate zones are de-
ciduous; those of the other zones, evergreen.

327. Steppes—When the moisture is not well
distributed throughout the year, but the rainfall

is periodical, and long droughts occur in the in-*

tervals between the rainy seasons, the forests are
replaced by areas called steppes, which, during
the wet seasons, are covered with grasses, shrubs,
or herbs; but during the dry seasons are almost
destitute of vegetation. Steppes are found in the
Llanos and Pampas in South America, in the
Great Plains of North America, in the grassy
steppes of Australia, Russia, and Asia, in the
German heaths, and in the African savannas.
828. Meadows and Prairies.—These, like the
preceding, are covered with tall grasses, but the
vegetation is more permanent, the droughts being
only occasional. They are found, therefore, in the
temperate zones, in the regions of constant rains.
An extended prairie region is found in the valley
of the Mississippi, on both sides of the stream.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 108. Desert Scene,

329. Deserts are regions characterized by an
almost entire absence of vegetation; they are
found mainly in the zones of the trade winds,
and are to be ascribed entirely to the absence
of moisture. Their bare surfaces are subject to
great and sudden changes of temperature, being,
as a rule, excessively warm during the day, and
often quite cool at night. These changes are

 

 

due to the readiness with which a bare surface
receives and parts with heat.

—10$840-e—_—_.

CHAPTER II.
Cultivated Plants.

830. Plants appear to have been originally
confined, by conditions of soil or climate, to cer-
tain localities. In many instances, however, plants
furnishing materials for food, clothing, or other
staples for the human family, have been trans-
planted and widely diffused by man. In most of
these cases, their successful cultivation is limited
to regions where suitable climate and soil ex-
isted either naturally, or have been artificially
produced.

331. Distribution of the Cereals—The cereals
include barley, rye, oats, wheat, maize or Indian
corn, and buckwheat; together with the potato,
they form the more important food-plants of the
temperate zones.

Barley, thought to be a native of Tartary and
Sicily, can be grown farther north than any other
grain; in Lapland, as far as 70° N. lat.

Rye is found as far north as lat. 67° N. in Nor-
way. It is the most common grain in Russia,
Germany, and in portions of France.

Oats is probably a native of the Caucasus; its
northern limit in Norway is about 65° N. lat.

Fig, 109, Maize, or Indian Corn,

Wheat is probably a native of Tartary. It is
the most important of the cereals, and has a wide