xxvi CONTENTS 



PAGES 



Kansas according to Hitchcock ; in Nebraska according to Pound and Clements. The steppe 

 in the Black Sea district according to Rehmann. The high-steppe near Alexandrovsk according 

 to Gruner ............... 591-603 



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 subter- 

 ranean 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 plateau 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 . 604-650 



CHAPTER X. EDAPHIC INFLUENCES IN THE TEMPERATE 



ZONES 



1. General Considerations. 2. Temperate Littoral Formations. Littoral swamp, 

 littoral meadow, dunes. 3* Heath. Calluna vulgaris. Conditions of existence. Companion- 

 plants. 4. Moors. High-moor and meadow-moor. Sphagnum. Conditions of nourishment. 

 Carnivorous plants of the American moor ......... 651-662 



SECTION III. THE ARCTIC ZONE 



CHAPTER I. GENERAL CHARACTERS OF THE ARCTIC CLIMATE 

 AND ITS EFFECTS ON VEGETATION AND FLORA 



1. General Characters of the Arctic Climate. General features. Summer temperatures. 

 Difference between the temperature of the air and that of objects exposed to insolation. Atmo- 

 spheric precipitations. Meteorological tables. 2. Effects of the Arctic Climate on Plant-life. 

 i. Survey of the Climatic Factors, ii. Vegetative Season and Periodic Phenomena. Conditions 

 of existence of plants in the arctic regions according to Kjellman. Awakening of vegetation from 

 its winter sleep. Middendorff's observations. Ripening of fruits, iii. Growth and Metabolism 

 of the Vegetative Organs. Stunted growth. Growth under continuous and interrupted illumi- 

 nation. Assimilation in continuous sunlight. Histological peculiarities caused by continuous 

 illumination, iv. Xcrophilous Structure of the Vegetative Organs. Xerophilous features caused 

 by the coldness of the ground. Cushion-growth, v. Reproductive Organs. Wealth of blos- 

 soms. Relatively large dimensions of the flowers. vi. Reputed Protective Measures against 

 Cold. 3. The Floristic Character of the Arctic Zone. The flora of Greenland according 

 to Warming. The flora of Spitzhergen according to Nathorst ..... 663-684 



CHAPTER II. ARCTIC PLANT FORMATIONS 



The Tundra. Characteristic features. Moss-tundra. Lichen-tundra. Moors. Oases. 

 The tundra in Taimyr according to Middendorff. The formations in Greenland. Warming's 

 classification 685-689 



