382 INTRODUCTION TO PLANT GEOGRAPHY [CHAP. 



similar in the different sectors into which the Arctic may conveniently 

 be divided {see Fig. 46). Thus the vegetation developed under 

 similar habitat conditions in any particular climatic belt ranged 

 around the top of the globe tends to look much the same in whatever 

 sector it may lie, and there do not seem to be any major subsidiary 

 regions that can be singled out, such as the Mediterranean or various 

 semi-deserts in the temperate zone. 



Under the prevailing cool conditions, water is very widely 

 sufficient in the Arctic for such limited growth as the climate, etc., 

 allows, and the main vegetational differences in any particular 

 belt are rather in accordance with the actual habitats (such as were 

 described in Chapter XI). Thus local edaphic or physiographic 

 variations can ring the most immediate and fundamental changes 

 in the local plant life. On the other hand a progressive and almost 

 regular over-all depauperation of the vegetation is to be observed as 

 we go farther and farther north ; and as this tends to be rather 

 closely comparable in the various sectors, it is deemed expedient to 

 separate each sector (and consequently the Arctic as a whole) roughly 

 into three main belts. These are the low-Arctic, in which the vegeta- 

 tion is continuous over most areas, the middle-Arctic, in which it is 

 still sufficient to be widely evident from a distance, covering most 

 lowlands, and the high-Arctic, in which closed vegetation is limited 

 to the most favourable habitats and is rarely at all extensive.^ The 

 following outline account of the main vegetational types of the 

 Arctic will accordingly have, under each major heading, some con- 

 sideration of the expression of this type in each of these three belts, 

 ranging from south to north. Examples of low-arctic lands are the 

 southern portions of almost all sectors, of middle-arctic lands Jan 

 Mayen Island and the vicinity of Point Barrow, Alaska, and of high- 

 arctic lands the whole of the Spitsbergen Archipelago, and the 

 Canadian Eastern Arctic north of Lancaster Sound. 



Arctic Tundras 



The term ' tundra ', meaning essentially a treeless plain, has been 

 used in so many and often such vague senses that it seems desirable, 

 if we are to retain it at all, to limit its use so that it will have a more 

 precise scientific connotation. In the present work the tundra 

 proper is understood as the usually ' grassy ' formation lying beyond 

 (or in some extra-arctic places forming patches within) the limit of 



^ See Frontispiece for a first, tentative attempt to delimit these three arctic belts. 



