21 



other, and here the snow lies long, is herb-field with the vegeta- 

 tion reduced to a turf, so that plants of the mat-form are mats 

 no longer, e.g., Helichrysum prostratum has its densely-leafy 

 silvery shoots dotted about, but not spreading and forming a 

 thick mat. Here and there are very small shrubs of Veronica 

 buxifolia. 



On Mount Ollivier (Sealey Range) at an altitude of 4200 

 feet and upwards are here and there hollows where the snow 

 lies until the beginning of February, and later. Such hollows, 

 as the snow melts, are bathed with ice-cold water for several 

 days at a time. Their vegetation differs from that of the 

 adjoining slopes where the snow melts much earlier. At about 

 4300ft. there are, in such hollows, mats of Danthonia oreophila 

 var. elata, perhaps lOin. thick, and so dense that hardly any other 

 plants can gain a footing. At a higher altitude there are masses 

 of Astelia nivicola flattened to the ground, and cushions of the 

 silvery Celmisia Hectori, which apparently, on this mountain is 

 confined to this station. On the adjacent slopes is tall tussock- 

 grassland of Danthonia flavescens, and its accompanying plants. 

 At a higher altitude this tussock is replaced by D. crassiuscula. 



On the flat summit of the Old Man Range (South Otago 

 Botanical District), at an altitude of 5000 feet and upwards, 

 the winter-snow lies long, and late snow-storms are frequent. 

 The ground, owing to the large quantity of snow-water, and the 

 powerful winds, is cut into hummocks some 9in. high, which 

 are covered with cushions of various species (e.g., Dracophyllum 

 muscoides, Phyllachne rubra, Raoulia Hectori, Hectorella 

 caespitosa, Veronica dasyphylla), and there is abundance of the 

 shrubby Celmisia ramulosa. After the snow melts the plants 

 are subjected to the full fury of the south-west gales hence, 

 apart from the snow-covering, the prevalence of the cushion- 

 form. 



A good many species are usually not met with until the line 

 marking the average limit of the winter snow is encountered. 

 Certain species of Celmisia, especially C. Haastii, and C. viscosa 

 are excellent indications of the snow-line, as, also in certain 

 parts of the North-eastern and North-western Botanical Dis- 

 tricts, the remarkable mat-forming grass, Danthonia australis. 

 Apart from the excess of ice-cold water which the plants are 

 obliged to tolerate, they are subjected to great pressure, and are 

 so flattened to the ground that one seeing them for the first time 

 could hardly believe they would recover. Plants forming dense 

 mats such as the two grasses mentioned above, are admirably 

 suited for their yearly burial, and their form may be considered 

 epharmonic. 



(f) Effect of the edaphic factor on plant-distribution. 



The edaphic factor, or to use Warming's term, "the nutrient 

 substratum 2 * ," is here used in the widest acceptation, and in- 



21- Oecology of Plants, 1919, p. 40. 



