214 The Plant Formations of the High Mountains. 
between the shrubs may be bare, but usually there is a sparse growth of tussock 
‚and some of its accompanying plants where there is forest rather than steppe- 
climate Discaria may develop into a low tree with stout trunk. 
2: Deissbertim recurvum-steppe. 
Phis association occurs only on the Volcanic Plateau and mountains ad- 
 jacent, and ranges in altitude from about 1080—ı 350 m. Though distinct 
enough, it merges into tussock-steppe, scrub and desert, indeed between it 
and the latter no hard and fast line can be drawn. The dominant plant is 
een recurvum which forms rounded cushions, or low mats, 6ocmin. 
. and 10-60 cm deep, made. up of ch brifiching rigid stems bearing 
_ semi-rosettes of strongly recurved, reddish-orange, stiff leaves each from 
2 „1.23. 8 cm long. The habitat is sbohar xerophytic. The soil, to a great 
Eee is merely pumice, scoria and andesitic lava mixed with sand from their 
isintegration. Where level, and sufficient plants are present, there is a layer 
ur sand 2.5—5 cm deep, black in colour through admixture of humus. But. 
the conditions for oxidation are usually too good and but little humus can 
 accumulate, while the dryness of the surface leads to its being, blown away. 
The water-holding capacity of the soil is of the slightest, and the water-table 
lies er below. the surface, moreover the evaporating action of sun and wind 
mes strorn ely into: Dr On ac cloudless summer day, when insolation reaches 
the becomes omes burning hot to the naked hand and 
netrates. markediy for at least —8 cm. The plants themselves 
1e ii fluence in supplying shade, making humus, and in the case 
