230 The Plant Formations of the High Mountains. 
bers of the formation are the species of Zpilobium and Raoulia') with E. melano- 
caulon characteristic of the dry areas and E. glabellum of the wet. Other 
common species are the grey, low shrub Helichrysum depressum half-dead looking 
with rigid stems and scanty small appressed leaves; - great eircular mats of 
Muehlenbeckia axillaris;, several species of Acaena; Veronica Lyallü in the wet 
and V. Bidwillii in the dry areas or stations; Helichrysum bellidioides, Coriaria 
thymifolia; C. angustissima (where abundant rain), Veronica catarractae (Fiord 
district), Angelica montana, Discaria toumatou and Raoulia glabra. Raoulta 
: Haastii, which forms large green cushions, is the characteristic plant of many 
river-beds in the Eastern and Western districts and occasionally occurs in the 
South Otago district. 
Subalpine torrent beds of the wet mountains, especially near their sources 
contain more or less of the fell-field and herb-field species and their open plant- 
covering may resemble that of the adjacent fell-fields. So, too, the old bed 
of the wider valleys often has a considerable florula and the association may 
be closed, but it is generally rather steppe dotted with shrubs than fell-field. 
Veronica Baröfeolin var. odora and Carmichaechia grandiflora are common in 
this association in the drier ku Southern Alps. | 
E: Fan. 
In the drier mountain areas, more Senestallye, where gullies or gorges open 
out on to plain or river bed, there are fans of debris, sometimes of great size. N 
Their vegetation depends upon the supply of stones brought down by the tor- 
rent and this again is correlated with the age of the gully and the plant-cov- | 
ering of its walls. Fans may be either active or passive, and every transition 
between the two can be seen. The stony surface is much steeper than that 
of river-bed in general. There are water-channels but these are usually dry 
_ except during heavy rain, the actual stream running underground. Many of, 
‚the stones are large and much of the debris coarse and piled up into compa- = 
ratively high but quite unstable terraces liable a flood to damage or 
absolute destruction. 
The vegetation is that of river-bed and: commences with the N species 
of Epilobium and Raoulia, Finally tussock steppe or Discaria scrub may be 
established but the intermediate stage may possess many circular mats. af. 
' Mnuehlenbeckia axıllaris and extensive ERBETEN ® ng ferns Blechmum Dame 
marina ‚and KRINRE, mällefohium. N 
5 Grass and Herb Formations. 
208 General. N e 
es The äistinction between grass and herb formations may seem at } first 
i ker ary, since Bee are, none EM the associations that do not contain 
