410 INTRODUCTION TO PLANT GEOGRAPHY 



mountains are ascended, fairly luxuriant if limited patches of more 

 or less closed vegetation are to be seen in some places up to altitudes 

 of at least 700 metres. Around such altitudes extensive grassy 

 tundra can occur in middle-arctic regions, as it can even higher up 

 in low-arctic regions — where, on the other hand, extraordinary 

 barrenness may already prevail lower down. Indeed remarkably 

 drastic variation is apt to be found in arctic uplands, often from 

 spot to spot in closely contiguous areas. Thus while in one place 

 the aspect is as of a plantless desert, in another there are plentiful 

 hardy rosette and other herbs such as Saxifrages and Arctic Poppy 

 {Papaver radicatiim s.l.), while in favourable situations a more or 

 less continuous tundra may prevail, or even a closed ' heath '. In 

 general, something approaching most lowland communities persists 

 well up into the mountains in the Arctic, while even near glaciers 

 or perennial snow, and at quite high altitudes and latitudes, the 

 climber may be agreeably surprised by a considerable show of 

 vegetation including herb- or moss-mats, and even heaths or flower- 

 slopes in the South. However, at very high altitudes even towards 

 the southern boundary of the Arctic, extreme barrenness is usually 

 encountered, with much snow and neve persisting through the 

 summer wherever the local topography allows, and little else save 

 crustaceous and foliose ' Tripe de Roche ' and other Lichens on the 

 exposed rock faces (Fig. 135). 



In temperate regions the zone of tundra, etc., just above the 

 timber-line is in many ways comparable with low-arctic regions 

 near sea-level, while higher up in both instances a similar sequence 

 of altitudinal climaxes prevails. Thus tundras of various types 

 roughly comparable with those of the Arctic are found above the 

 elfin wood to the south, with often extensive tracts of scrub (Fig. 

 136, and cf. Fig. 115) where conditions are suitable and pasturing 

 is not too severe. Above this may stretch increasingly limited tracts 

 of ' alpine meadow ' consisting of short and more or less matted 

 Grasses, Sedges, and forbs or under-shrubs (Fig. 137, A) ; heathlands 

 may develop in particularly favourable situations, and fell-fields or 

 barrens in detrital or exposed ones. Mossy mats are especially 

 characteristic of run-off areas below snow-banks hereabouts. 



Still higher up and nearer the Equator there is not merely a rigorous 

 climate to contend with but, also, geodynamic influences which are 

 often powerful, so that conditions and the attendant vegetation 

 may vary considerably from spot to spot. Almost all the vascular 

 plants persisting here are chamaephytes or hemicryptophytes, and 



