southward into the province of Coquimbo a gradual change in the arid
conditions may be observed. The higher summits of the Cordilleras
afford a larger and more continuous supply of water, and so dependent
are the people in the cultivated river valleys on this source of water
supply that they watch for snowstorms in the Cordilleras as an
indication of what the coming season is to be. The arborescent growth
near the mountains is larger and more vigorous, in which are to be
found the "algarrobo" (_Prosopis siliquastrum_) and "chanar"
(_Gourliea chilensis_), but the only shrub to be found on the coast is
a species of _Skytanthus_. Near the sierras where irrigation is
possible, fruit-growing is so successful, especially the grape and
fig, that the product is considered the best in Chile. In regard to
the indigenous flora of this region John Ball[2] says: "The species
which grow here are the more or less modified representatives of
plants which at some former period existed under very different
conditions of life." Proceeding southward cacti become common, first a
dwarfed species, and then a larger columnar form (_Cereus quisco_).
The streams are fringed with willows; fruit trees and alfalfa fields
fill the irrigated valleys, and the lower mountain slopes are better
covered with a thorny arborescent growth. The divides between the
streams, however, continue barren as far south as the transverse
ranges of mountains across the province of Aconcagua.

To some degree the flora of central Chile is of a transition character
between the northern and southern zones. It is much more than this,
however, for it has a large number of genera and species peculiarly
its own. A large majority of the 198 genera peculiar to the South
American temperate regions belong exclusively to central Chile. This
zone extends from about the 30th to the 36th parallel, perhaps a
little farther south to include some characteristic types. The
evergreens largely predominate here as well as in the extreme south,
and on the open, sunburnt plains the vegetation takes on a subtropical
aspect. One of the most characteristic trees of this zone is the
_peumo_ (_Cryptocarya peumus_), whose dense evergreen foliage is
everywhere conspicuous. The _quillay_ (_Quillaja saponaria_) is
another characteristic evergreen tree of this region, whose bark
possesses saponaceous properties. In earlier times the c