CHAPTER IX 

 DESERTS 



Introduction. Distribution and climate of deserts in general, i. The Deserts of the 

 Eastern Hemisphere, i. The Desert District of North Africa and South- West Asia. 

 Extent. Climate. Character of the country. Flora of the spring rain. Significance of 

 subterranean water to vegetation. Protective devices of plants against the loss of water. 

 Desert formations in Equatorial East Africa, ii. The Desert Districts of West and 

 Central Asia. Climate. Characteristic plants. Physiognomy of deserts near the 

 Caspian Sea. iii. The Desert in South Africa. Extent. Climate. Character of vegetation 

 in the littoral desert, and in the Karroo. Welwitschia mirabilis. Acanthosicyos horrida. 

 iv. The Desert in Australia. 2. The Deserts of the Western Hemisphere, i. The 

 Desert in North America. Extent. Climate. Lower Sonoran region. Characteristic plants. 

 Oases. Upper Sonoran region. Protective devices against drought. Flora of the 

 spring rain. The ' Bad Lands' in Dakota and Nebraska. Desert plateaux at the eastern 

 base of the Rocky Mountains, ii. The Desert and Semi-Desert in Mexico. Climate. 

 Character of the vegetation according to G. Karsten. iii. The Desert in South America. 

 Physiognomy of the Patagonian desert according to Niederlein. 



INTRODUCTION. 



The most extensive deserts occur near the two tropics, which they over- 

 step only slightly towards the equator, their greatest development being on 

 the polar side. For this reason, and also because we are better acquainted 

 with the vegetation of the temperate than with that of the tropical deserts, 

 this chapter will deal with the climate and vegetation of deserts in general. 



The greatest desert district extends from the Atlantic coast of Africa, 

 between 20° and 30 N., right across the whole continent, widening out 

 occasionally to the north, over Arabia, South Persia and Baluchistan, to the 

 north-west corner of Hindustan. The second greatest desert district includes 

 a large part of Central Asia, from the Caspian Sea to the mountains sepa- 

 rating Mongolia from Manchuria. North America possesses a smaller 

 desert district lying between 30 and 40 N. and 120 and 11 2° W., to 

 which the States of Utah, Nevada, part of Arizona, and Southern California 

 belong, and continuing into the semi-desert of the Mexican plateau. The 

 greatest desert in the southern hemisphere is that of Central Australia ; 

 smaller deserts occur in South-West Africa, in the narrow western strip of 

 South American coast from 5° to 30° S., also in West Argentina and in 

 Eastern Patagonia. 



