Rock Associations. 223 
in a moist climate both on flat rocks and in depressions and hollows, so that 
a plant-covering may eventually be established not to be: distinguished from 
that of the adjacent herb-field. At the same time, there are some species that 
especially affect soil-covered rocks and are ‚almost confined thereto‘).. The 
number of species fairly common on rocks is 161 belonging to 36 families 
and 72 genera. This estimate is not of much moment, since many wet-mountain 
plants are here excluded which, in one place or another, grow on rocks. Far 
more important is it, that 45 species appear to be confined to rock of which 
36 are purely mountain-plants. They may be classified as follows: — - Shrubs 17; ka 
semi-woody 8; herbs 16; grass-like 2 and ferns 2. Cushion-plants. number at er 
least ı2 (26 p. c.) and some of the other growth-forms are at times ch3 = 
to cushions; rosette-plants number ı1, some most closely pressed to the rock, Br 
and ra shrubs 5. The leaves of 16 are tomentose or distinctly ri Hs 
Five species’of Raoulia of cushion-form, 3 of Helichrysum of cupressoid-form, 
their leaves woolly and the rigid, excessively thick-leaved Acipkylla Debsonk: E 
_ are intensely xerophytic, but the remainder, though generally xerophytic enough, a 
are not more so than many other alpine plants, and it is hard to guess why 
they should be confined to rock, in many cases always dry, especially as ERpeE 
can be cultivated readily in ordinary Ben soil. 
db. The Korkiarsskuhiehe. 
ı. The North Island Volcanoes. ae 
Here there are no special rock-plants. The ee is scanty and) 1 
Ä braite mosses and lichens consists only of deep-rooting desert or steppe 
 xerophytes, especially — Danthonia semiannularis var. setifolia, Poa Colenson, 
 Amisot otome aromalica, Gaultheria a and ee, dell dio des® 
