practically uninhabited by
man. Each is peopled only by primitive nomadic hunters who stand at the
very bottom in the scale of civilization.

Aside from the rain forest there are two other types in tropical
countries--jungle and scrub. The distinction between rain forest,
jungle, and scrub is due to the amount and the season of rainfall. An
understanding of this distinction not only explains many things in
the present condition of Latin America but also in the history of
pre-Columbian Central America. Forests, as we have seen, require that
the ground be moist throughout practically the whole of the season that
is warm enough for growth. Since the warm season lasts throughout the
year within the tropics, dense forests composed of uniformly large trees
corresponding to our oaks, maples, and beeches will not thrive unless
the ground is wet most of the time. Of course there may be no rain for a
few weeks, but there must be no long and regularly recurrent periods of
drought. Smaller trees and such species as the cocoanut palm are much
less exacting and will flourish even if there is a dry period of several
months. Still smaller, bushy species will thrive even when the rainfall
lasts only two or three months. Hence where the rainy season lasts most
of the year, rain forest prevails; where the rainy and dry seasons do
not differ greatly in length, tropical jungle is the dominant growth;
and where the rainy season is short and the dry season long, the jungle
degenerates into scrub or bush.

The relation of scrub, jungle, and rain forest is well illustrated in
Yucatan, where the ancient Mayas reared their stately temples. On the
northern coast the annual rainfall is only ten or fifteen inches and is
concentrated largely in our summer months. There the country is covered
with scrubby bushes six to ten feet high. These are beautifully green
during the rainy season from June to October, but later in the year
lose almost all their leaves. The landscape would be much like that of
a thick, bushy pasture in the United States at the same season, were
it not that in the late winter and early spring some of the bushes bear
brilliant red, yellow, or white flowers. As one goes inland from the
north coast of Yucatan the rainfall increases. The bushes become taller
and denser, trees twenty feet high become numerous, and many rise thirty
or forty feet or even higher. This is the jungle. Its smaller portions
suggest a second growth of timber i