The ecologieal Conditions of the High Mountains. 179 
plants such as Celmisia spectabilis may be killed by drought., In short, many 
species obviously depend far more upon precipitation than upon ground-water 
and, in this regard there is a similarity between rain-forest and herb-fel 
The N.W. rain, on which depends the distribution of many RR in 
the South Island, is a warm snow-melting rain, whereas that from the S.W. 
‚is cold and generally terminates in snow, succeeded by frost. This latter rain, 
‚in South Otago and Stewart Island is a most important factor towards inducing 
 herb-field and moor. Its frequent occurrence, combined with cloudy skies, 
 brings in those subantarctic conditions which even in the lowland favour alpine 
' plants. On the slopes of the Southern Alps facing the Canterbury Plain and 
on the Seaward Kaikoura Mts. much rain comes from the E. 
0 Snow is a most important factor in New Zealand high mountains. er EN 
been already shown how the primary division of the vegetation into belts de- 
- pends upon the winter snow-fall. The amount that collects in gullies &c. must 
be very great. When the upper mountains are almost bare, at the end of 
January or later, in the Western, Fiord and South-Otago districts, great masses. 
at times resembling glaciers still lie in cirques and gullies., Snow-avalanches 
‚are extremely frequent, even on the driest mountains, and their effect is indeed 
5 great in destroying vegetation and furthering denudation (Plate XXXV, Fig. 47). 
In the alpine belt the vegetation after the snow has melted looks just as #8 
steam-roller had passed over the surface, so flattened to the ground are the 
reflected by the presence of special species and combinations of plants. The 
mechanical effect of a heavy snow-covering upon the subalpine-scrub may be 
pointed out, but it alone is not responsible for the peculiar growth-forms. x 
The wind-factor is of great moment, acting as it does both mechanically ah 
and Physiologically upon the plants, while as an agent of. er it iS ‚A 
i 1 beti en | 
plants. The effect of temporary streams and pools, or of snow-water in hollows, 
