a 
i es ae ae 
7 
have a very slight: rain-- 
as deserts (Figs. 48, 
ee a Ce Se ee ee eee SS eee a eee 

PLANT GEOGRAPHY 453 
usually without trees except along watercourses. In the United 
States the more moist grassland or prairie is excellent for raising 
grain, while the drier grassland or plain is good for grazing. 
In many cases extensive grasslands are due to the interference 
of man rather than to natural conditions. In temperate regions 
meadows are frequently 
produced as a result 
of cultivation. In the 
Malay Archipelago large 
tracts of rank, waste 
grasslands are due to 
periodic fires which have 
followed the removal 
of the original forests. 
The fires destroy dicoty- 
ledonous plants but do 
not appreciably damage 
the underground rhi- 
zomes of the grasses. 
Similarly, fires are fre- 
quently responsible for 
the presence of grass- 
lands in temperate areas. 
Deserts. Areas which 

fall and are covered by 
a scanty growth of scat- 
tered plants are known 
Fig. 508. Epiphytes on trunk near the upper 
limit of two-storied forest on Mount Maqui- 
ling, Philippine Islands 
D911). The largest area stretches across Africa into south- 
eastern Asia. In Africa it is called the Sahara Desert, and in 
Asia it is called the Arabian Desert. The next largest area in- 
cludes most of central Asia. Large desert areas occur in central 
Australia and in Mexico and the western part of the United 
States, while small areas are found in southwestern Africa and 
South America. 
