90 NEW ZEALAND PLANTS. 
Amongst the earliest settlers are the willow-herbs (Hpilobium), 
thanks to their light seeds furnished each with a tuft of hairs and so 
readily the sport of the wind. Various species of Raoulia come in 
a similar manner, and large, circular, moss-like cushions or patches of 
silver and green result (Raoulia australis, R. lutescens, R. tenuicaulis, 
R. Haasin) (figs 53, 54). Lichens cover the stones with curious 
markings, and mosses spring up on the silt. As these earlier plants 
decay, humus is added to the silty, sandy soil, and, as already 
explained, various drought-resisting shrubs—Discaria towmatou (this 
frequently forming thickets of itself alone) (fig. 55), Cassinia fulvida 
var. montana, species of Carmichaelia—put in an appearance, together 
with grass-tussocks. Such shrubs may remain quite isolated, and the 
tussock become dominant, in which case the shelter will favour the 
settlement of many small herbaceous plants, including grasses, and 
grassland will result (fig. 55). Or, on the other hand, the con- 
ditions may favour arborescent growth —a natural shrubbery of 
koromikos, coprosmas, and other shrubs, some with wiry branches, 
may appear, perhaps to be replaced finally in the mountains by a 
southern-beech forest. Grassland formed in this manner may be 
seen in process of evolution in many places, and it was in this 
way that the great river-made plains, equally with the “fans” of 
debris at the outlet of creeks, have been colonized by their plant 
inhabitants. 
The red-tussock (Danthonia Raoulit var. rubra) is considerably 
taller than the silver or the hard tussock, being 23 feet high or more. 
The stems and leaves are bunched closely together to form the base 
of the tussock, which is about 1 foot through; but they spread out 
above and bend downwards near their tips, and there the tussock 
will be more than twice the diameter of its base. The leaves are 
narrow, thick, and leathery; their sides are bent inwards, and they 
taper to a fine long drawn-out point. The colour is green tinged 
more or less deeply with orange or red. The stout leaf-sheaths 
remain part of the tussock after the narrow blades are decayed, 
forming a close covering round the stem many times larger than 
the living portion. There is a short woody rootstock, provided 
with rather long wiry roots. 
The ground occupied by this grass and its associated plants is 
usually more or less wet ; indeed, in Southland, where it still occupies 
fairly large areas, the plant-association follows after sphagnum bog. 
