204 The Plant Formations of the High Mountains. 
N. Menziesüt, may form the lowest belt and N. c/iffortioides, either pure or 
mixed with NV. Menziesü, the highest. The effect of station on the distribution 
of these species is sometimes striking. Thus, according to F. G. GIBBS, on one ' 
part of Mt. Arthur (North-western district), in the subalpine N. Menziesii forest, 
at an altitude of 1020 m, N. fusca gives out and N. chffortioides appears, but 
especially on dry, rocky points. In the extensive N. chffortioides forest 
near the sources of the River Poulter (Western district, eastern part), N. fusca 
appears occasionally, but it is invariably confined to sheltered gullies, 
where the conditions are much more mesophytic than on the ridges and slopes. 
2. Mountain-beech (N. cliffortioides) forest. 
General. 
This association rarely descends, even in the South Island, to much below 
600 m. The most extensive areas occur on the Volcanic Plateau: Ruapehu and 
the Kaimanawa Mts. (North Island) and from the North-western to the North 
Otago botanical districts (South Island). Elsewhere, the association is often ' 
wanting, or it occurs merely in patches, or a narrow belt, at the upper limit 
of the forest. Where there is an abundant rainfall, the association is continuous 
with montane forest, but where steppe-conditions prevail, it is generally confined 
to gullies, hollows, or the sheltered side of river-terraces. In such cases, there 
is no merging of forest and steppe, but the tree-mass ends abruptly. 
The relative abundance of species, and the physiognomy of the forest, at 
any particular point, depends on latitude, climate and soil. In the South Island, 
according as the precipitation favours forest or steppe, so are there two cases 
of the association, here termed “wet” and “dry” respectively. 
About 39 species belonging to 21 families and 26 genera are fairly. common 
in this association, and these comprise, — ı forest-tree, 18 low trees and shrubs, 
1 woody = 2 woody parasites, 7 herbs, 4 gras like plants and 6 ferns and 
lyeopods. But, there are many plants not included in this estimate, for, at 
5 the upper limit. of, ans Dreh, subalpine-scrub plants enter in, and at the lowest 
y not nearly so dense. as that of tän- free 
and is made up of but Fan species. Tree-ferns are wanting, unless Polystichum 
vestitum be so considered, while the smaller ferns are poorly represented both 
in Dr and individuals, Woody lianes are of no moment, one or other ® 
= BER SEN, ie The trees do not raise their roots high AI the gro 
is no sontinuous” Kr small trees. Aa above the a 
mon members. of the association. \ Through 
22 Zum. mm, olepis m chmum 
