BOTANICAL GEOGRAPHY 325 
regions very abundant (over sixteen feet of rainfall in a 
year) or sometimes, in desert areas, almost lacking. We 
find here, accordingly, the greatest extremes in amount 
of vegetation, from the bare sands or rocks of the Sahara 
desert (Fig. 229) to the densely wooded basin of the 
Kongo and of the Amazon. Xerophytic plants, many of 
them with extremely complete adaptations for supporting 
life for long periods without water, are characteristic of 
tropical deserts, while many of the most decided hydro- 
phytes among land-plants are found in the dripping sub- 
Fic. 229. — Hills of Drifted Sand in the Sahara. 
tropical forest interiors. Throughout a large part of the 
zone, reaching five degrees each way from the equator, 
there are daily rains the year round. 
397. Vegetation of the Temperate Zones. — We are all 
familiar in a general way with the nature of the plant 
life of the north temperate zone; that of the south 
temperate is in most ways similar to our own. Most of 
the annuals and biennials are of a medium type, not 
decided xerophytes nor hydrophytes, and the perennials 
are mainly tropophytes. ‘There are no desert areas so 
large or so nearly destitute of plants as those found in 
subtropical regions, neither are there any such luxuriant 
