266 The Vegetation of the Subantarctic Islands. 
The distribution of the New Zealand element according to botanical pro- 
vinces &c. is: Kermadec ı2 (7 pteridophytes); Chatham 42 (20 pteridophytes) 
Northern 65 (25 pteridophytes); Central 96 (pteridophytes 29); Southern (ex- 
cluding Stewart district) ıı2 (pteridophytes 31); Stewart district 105 (pterido- 
phyta 33). 
The vertical distribution of the New Zealand element for the remainder 
of the region is: — Coastal 21; lowland 2ı; common to both lowland and 
alpine 47; alpine except at times in far S. ı8 and purely alpine 16. 
db. The ecological conditions. \ 
The climate is uniform; there is but little difference between the means 
or extremes of winter and summer temperature. The sky is generally cloudy; . 
showers are frequent; the atmosphere is saturated; periods of sunshine are brief; 
there is a general average low temperature with but slight winter frosts at sea- 
level; cold and violent winds accompanied by showers of sleet, hail or even 
snow are of constant occurrence. The wind indeed is a master-factor. Its mark 
is on the vegetation everywhere both in regard to form and distribution. The 
moisture-laden air and lack of sunshine favour the formation of peat. Dead 
stems and leaves of the herbaceous plants, slowly rotting, remain attached 
to.the living plants. Bryophytes on the ground, on tree-trunks and on rock- 
faces build thick layers and cushions of peat, the outer shoots alone alive. 
The ferns, Blechnum durum and Asplenium obtusatum of the coastal cliffs form, 
from their dead rhizomes, masses of peat, 30 cm or more in depth, which‘ 
completely cover the flatter rocks. The soil of all the islands, indeed, for a 
depth of 9 m, or more, is made up alltogether of plant-remains. Such a soil 
becomes saturated; pools lie on the surface and holes, masked by vegetation, 
full of water, are frequent on the open hillsides. The indigenous birds, espe- 
 cially penguins and albatrosses, and the seals, in some of the small islands, 
play an important part in sn -distribution and where numerous bring about 
a regular “rotation of crops” (Plate LVI, Fig. 86). 
2. The leading Physiognomic Plants and theik Growth-forms. 
With the exception of the Metrosideros, the following physiognomic plants, 
common to the Subantarctic province and the main islands of New Zealand, 
‚need no description: — The’herbaceous and filmy ferns, especially Polystichum 
vestitum; Metrosideros lucida; Nothopanax simplex; Dracophyllum longifolium;, 
 Suttonia divaricata and Coprosma Joetidissima. : 
M. Iucida (Myrtac.), the southern rata or ironwood i is, in New Zealand 
.  Proper, an erect, evergreen tree with a maximum height of some ı8 m, butin 
Lord Auckland’s Islands the trunk is nearly always prostrate (Plate LVII, Fig. 87) 
more or less, irregular in shape,:bent or arched and far-spreading either on, 
or just above the forest-floor. The branches, too, are gnarled and twisted and 
extend more 'or less ‚horizontally at first, but finally put forth erect branches 
which Puuacle terminate in numerous An bearing.; Abu oh and so 
