Adaptations of the Alpine Plants.

High mountain plants live under conditions considerably different from those of the lower country. The climate is much colder, many are buried beneath a great depth of snow for several months, and all are subjected to frost at any period of the year. The atmosphere is more rarified than, at lower levels, and this leads to stronger and more active sunlight, and to a more rapid loss of water from the leaves of the plants. Although the mountain climate is a wet one, yet when the sun is shining and the sky clear the plants are exposed to danger of damage from a too rapid loss of water. Nor are several page 101

Fig. 49.—Veronica spathulata, growing on scoria desert, base of Ngauruhoe.
Lands Department.] [Photo, L. Cockaync.

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Fig. 50.—The North Island Edelweiss (Helichrysum Leontopodium).
[Photo, W. C. Davies.

Fig. 51.—Helichrysum bellidioides, showing the white bracts of the flower-heads, which look like petals. Stony ground near Arthur's Pass.
[Photo, L. Cockayne.

page 103days of sunshine in succession, unknown even on the wet western mountains. In harmony with, this danger of drought, with, the cold of winter, with the heat of summer, and with the fierce wind-storms, the plants have developed, or preserved, special contrivances, or peculiar habits of growth, some serving frequently more than one purpose. Thus many plants are of most lowly growth. The genus Dacrydium, to which belong several lofty forest-trees, amongst others the rimu, is represented in the New Zealand mountains by a creeping-plant which grows at times so densely as to form an actual turf or a cushion (fig. 52). Many plants have the form of cushions, and very beautiful are the rounded green cushions of Phyllachne Colensoi and Donatia novae-zelandiae, especially when gemmed with multitudes of small white flowers.

Roots of an extraordinary length form an excellent provision for obtaining an abundant water-supply at all seasons, and these are very frequent amongst the alpine plants. But, above all things, the leaf, in structure and form, shows drought-resisting contrivances. The most common of all is a mat of hairs on the under-surface of the leaf, so characteristic of the celmisias (fig. 43). Some, again, such as the Aciphyllas^* (spear-grasses), have extremely rigid, vertical leaves, which both resist the wind and can never receive the direct rays of the sun.

Perhaps the most interesting feature of the New Zealand alpine plants, and one which is not so well marked in the alpine plants of Europe, but is seen in those of the Andes, is the capability of one portion of the living plant to turn into peat, while its remaining part grows vigorously, and even uses its own dead self as food material. This habit is not specially in harmony with an alpine climate, but rather with absence of sunlight and prevalence of rain and mist—just such a climate as exists in the subantarctic islands to-day. Most of the celmisias are surrounded at the bases of their leaves by quite a thickness of rotting leaves, and the same may be seen in a very large percentage of the New Zealand alpine plants. Such an adaptation perhaps indicates that our alpine flora originated not on the high mountains at all, but in the sunless and wet regions of the south.

Fig. 52.—The Dwarf-pine (Dacrydium laxifolium), which on the dry pumice soil has assumed the cushion-form Veronica tetragona, a Whipcord-veronica growing on it above, and small plants also of Celmisia longifolia. Volcanie plateau of North Island, at 3,700 ft. altitude.
Lands Department.] [Photo, L. Cockayne.