VEGETATIONAL TYPES OF POLAR LANDS 413 



a large proportion are obviously xeromorphic, being reduced in 

 stature, very hairy, or otherwise modified to conserve water. As 

 compared with those of lowland plants, the leaves tend to be smaller 

 and thicker, with a greater development of protective tissue. Indeed 

 the general aspect is much as in the Arctic, with hardy cushion or 

 rosette plants including bright-flowered Saxifrages often in evidence, 

 and Lichens and Mosses plentiful, any woody plants being excessively 

 dwarfed. However, more and more of the actual species tend to 

 be different as we travel south, until in the tropics very few arctic 

 inhabitants are left, although the general aspect may still be some- 

 what arctic-like at very high altitudes. Moreover, there are fre- 

 quently anatomical and other differences between arctic and alpine 

 plants even of very close systematic alliance. Fig. 137, B, shows a 

 wide range of plants flowering at an altitude of about 5,944 metres 

 {c. 19,500 feet) on Mohala Bhanjyang, West Nepal, in the Himalayas 

 — higher than flowering plants are commonly supposed to go in any 

 number, and perhaps constituting a record in this respect. The 

 genera are often represented in the Arctic, and at least one arctic 

 species, Lagotis glauca s.l., is visible. At lower altitudes in the 

 tropics and especially down near timber-line, the ' mountain grass- 

 land ' is often very luxuriant and inclusive of woody associates 

 which do not, however, normally reach a greater height than the 

 herbaceous cover, though in some places a tall scrub may occur 

 between the Krummholz and fell-fields. 



In some temperate and tropical regions, especially of an arid 

 nature, and in keeping with the general reduction of precipitation 

 at very high altitudes, dry conditions may prevail above the timber- 

 line. Here the effect of aspect is often particularly noticeable. 

 Thus in parts of central Asia, steppe-like vegetation may persist on 

 the southern slopes of mountains, while, on the shadier northern 

 slopes, more luxuriant alpine meadows often occur at similar altitudes. 

 In these meadows may be tall forbs, and on the slopes below are 

 often many trees — in marked contrast to the arid steppe-like com- 

 munities on the south-facing side {cf. Fig. 83, B). Elsewhere, xeric 

 grasslands in which the tussocks of the dominants fail to coalesce 

 may be common on slopes around 3,000-4,000 metres, below the 

 fell-fields, while on plateaux at similar or even higher altitudes, such 

 as the ' punas ' of South America and the ' pamirs ' of Tibet, ex- 

 tremely severe drought and temperature conditions may prevail and 

 the vegetation consist of sparsely scattered tufts of Grasses and 

 hardy cushion-plants (Fig. 138). In the high Andes of Peru, etc., 



