344 A TEXT-BOOK OF BOTANY 
typical one; and the Desert of Sahara is another well-known 
illustration. 
207. Thickets.—Xerophytic thickets are the most 
strongly developed of all thicket growths. They are spe- 
cially characteristic of the subtropics, and may be described 
as scraggy, thorny, and impenetrable. Such thickets are 
well displayed in Texas, where they are called “ chaparral’’; 
and similar thickets in Africa and Australia are spoken of 
as “bush” or “scrub.’”’ In all of these cases the thicket is 
of the same general type, and is one of the most forbidding 
areas for travel. 
208. Forests.—The most common xerophytic forests of 
the United States consist of conifers, especially of pines. 
They occur along the rocky slopes of the mountains, and 
on the vast sandy areas that border the Great Lakes and 
cover the Gulf States (Fig. 312). 
209. Salt steppes.—In these areas, not only are the 
drought conditions continuous, but the water is alkaline. 
The salt steppes are interior dry wastes which probably 
mark the site of old sea basins. In the United States one 
of the most extensive of the salt steppes is the Great Salt 
Lake Basin. Another extensive alkaline waste is known as 
the Bad Lands, which stretches over certain portions of 
Nebraska and South Dakota. 
210. Salt and alkaline deserts.—In these areas the 
water-supply is at its lowest ebb, and therefore is saturated 
with the characteristic salts of the soil. No worse com- 
bination for plant activity can be imagined than the com- 
bination of scanty water-supply and abundant salts. In 
consequence, such areas are almost, if not absolutely, devoid 
of vegetation. As illustrations, the extensive desert of the 
Dead Sea region and the Death’s Valley in southern Cali- 
fornia may be cited. 
