762 



ZONES AND REGIONS [Pt. Ill, Sect. IV 



the Andes, the structure is extremely xerophilous, and is particularly 

 expressed in the prevailing alpine form of cushion-plant. By reason of 

 their size and density, the most imposing of these are the ' vegetable sheep ' 

 of New Zealand, the woolly species of Raoulia (Compositae) (Fig. 466). 

 Helophyllum Colensoi (Candolleaceae) (Fig. 467) resembles them. Smaller, 

 but likewise extremely dense, cushions are formed by several species of 



Fig. 463. Aciphylla Colensoi, on stony ground near Lake Pearson; altitude 6oo meters. 

 South Island of New Zealand. From a photograph by Cockayne. 



Veronica, Hectorella, Dracophyllum. Celmisia viscosa (Fig. 464) forms large 

 but looser and flatter cushions. Luzula pumila (Fig. 464) also, by the dense 

 growth of its narrow leaves, approaches the cushion-form. There also 

 occur, as in all alpine situations, small creeping shrubs of marked xero- 

 philous structure (Fig. 40cS), and rosette-plants with long roots (Fig. 411). 



iii. AFRICA. 



The coast-land of Natal is composed of a series of broad terraces rising 

 by steps to the adjoining mountains. The plateaux are very open towards 

 the sea, are windy, and therefore unadapted for the growth of trees ; added 

 to that, Natal, owing to its dry winters and moist summers with frequent 

 falls of rain, possesses a typical grassland-climate. The increase in the 

 atmospheric precipitations, which in particular is exhibited in the upper 



