HorLowav.—Studies in the New Zealand Hymenophyllaceae. 71 
With regard to the forest-covering, it may Бе said generally that there 
is but the one type in Westland—namely, the very heavy mixed taxad 
rain forest. It is true that there are variations in this, such as the more 
open black-pine and white-pine stands of the river-flats, and the character- 
istic association of the higher mountain-flanks; but these can be regarded 
here as local varieties of the taxad rain forest. East of the dividing range, 
however, there is a considerable differentiation in the forest-covering, 
depending both upon altitude and upon general climatic conditions. The 
relation between the forest type and the soil-conditions cannot be entered 
into here. In Canterbury there is both rain forest and also dry southern- 
beech forest. On the eastern flanks of the dividing range the altitudinal 
factor is the stronger, and, although the rainfall is heavy, the rain forest 
is not taxed but mountain southern-beech. Cockayne and Laing have 
shown, however (16, p. 363), that at the source of the Rakaia River, 
on the eastern flanks of the main ranges, the mountain-totara and the 
kawaka form a very characteristic association which can be regarded as 
true western rain forest. I have preferred to consider the occurrence 
of the Hymenophyllaceae in this southern-beech rain forest apart from their 
occurrence in the Westland forests, although these two types of э ав 
they here occur belong to the same botanical district of L. Cockayne (14), 
and I have done this in order to reduce the problem of ther distri- 
bution in Westland as far as possible to the simple question of the effect 
upon the family of altitude alone. In South Canterbury the pees: х 
areas of rain forest lie at a lower altitude and are not southern-beech, 
mixed taxads. On account of the moderate rainfall, however, they are 
.less heavy than those of Westland, and lack a number of characteristic 
members of the Westland rain forest. In North acp where the 
north-west wind is most experienced, the dry southern-beech forest 
prevails, cu this dry wind, of course, may ifs rep he only cause 
determining its presence. Thus whereas in Westland the end distri- 
bution of the Hymenophyllaceae is dependent, on the whole, upon the 
altitudinal factor alone, east of the dividing range there must be con- 
sidered, in addition to the altitude, the type of forest present, and also 
the particular rainfall and general humidity conditions prevailing in each 
area of forest. 
Table A, indicating the difference in the climate experienced at the 
west and east coasts respectively, is taken from Part I of these Studies. 
A. The Eastern Flanks of the Southern Alps. — 
In my previous paper I have given a detailed account of the occurrence of 
the Hymenophyllaceae in the Otira Gorge and on the neigh 
tain-sides at the western extremity of Arthur’s Pass. I will now trace 
their distribution on the eastern side of the pass and on the eastern flanks 
of the dividing range in its vicinity (see maps on pages 73 and 76). 
The rainfall at the eastern portal of the Midland Railway tunnel which 
pierces the range at this point, distant a little over five miles from the 
western (or Otira) portal, is somewhat less than that recorded for the latter 
locality. As at Otira, the main continuous rain comes from the north- 
west. E accordance with its higher altitude (viz., 2,435 ft.), more snow 
falls in winter at the eastern end of the pass than at the western (1,583 ft.). 
The rainfall diminishes rapidly farther down the Bealey River valley 
which descends from the pass in a south-easterly direction, and at the 
junction of the Bealey with the main Waimakariri River valley, and in this 
