GROWTH-FORMS AND SPECIES OF BOGS. 125 
as that of the adjacent wet peaty soil, probably owing to the moss 
being saturated with fresh water after rain. Against the theory 
of cold water being the cause of the physiological dryness of 
bogs there is the case of drought-resisting plants being present on 
the comparatively warm bogs of North Auckland, where frost is 
unknown, and where the water can never become cold enough to 
check the action of the roots. 
The special structure and many of the growth-forms of bog-plants, 
as mentioned above, are similar to those of plants of the driest stations. 
Thus dwarfing is frequent; the manuka, for instance, becomes at 
times an almost turf-making plant. The swamp-heath (Dracophyllum 
paludosum) of the Chatham Islands, and even the purple tree-daisy 
(Olearia semidentata) of the same group, bloom when a few inches in 
height, though under ordinary circumstances the stature of the former 
is 6 feet and of the latter 3 feet. The cushion form is common on 
mountain-bogs, as in the alpine donatia (Donatia novae-zelandiae) 
and the common phyllachne (Phyllachne Colensoi). The tussock 
form, the rush form, the creeping form with an underground stem, 
and the rosette form all occur on bogs. These and other forms 
receive some consideration below. 
Attention can next be called to certain bog-plants and to the 
composition of various bog associations. The wire-rush (Hypolaena 
lateriflora), a brownish, wiry-stemmed, rush-like plant, is a most 
characteristic species, and forms from one end of New Zealand 
proper to the other end extensive pure colonies both on lowland 
and mountain bogs. So, too, one or other of the smaller umbrella- 
ferns (Gleichenia dicarpa, G. alpina) by its green colour makes a 
bog recognizable at a long distance (fig. 82). 
Many subalpine bogs are occupied principally by the following : 
A green cushion-plant, Phyllachne Colensoi ; Donatia novae-zelandvae, 
strongly resembling Phyllachne; the common oreobolus (Oreobolus 
pectinatus), a sedge of similar habit to Donatia, with leaves arranged 
like a comb; a small celmisa (C. longifolia var. alpina) and another 
with broader leaves (C. glandulosa); the slender grass Deyeuxia seti- 
folia ; certain plants belonging to the rather rare family Restionaceae 
—Gaimardia ciliata, G. setacea, and G. pallida, all cushion-plants 
(fig. 81), and looking like mosses. Here, too, will be in some localities 
a dense turf formed by a woody plant, the pygmy pine (Dacrydium 
laxifolium), that smallest species in the world of the pine-tree family : 
