118 TRANSACTIONS OF THE [SEss. LXxv. 
mediates between them exist, and the difference of one 
from the other is of degree merely. 
There is a central woody main stem and a deeply- 
descending chief root. From near the base of the stem a 
number of prostrate and rooting branches pass off radially. 
These branch abundantly in their turn, the divisions having 
a tendency to grow upwards, and this is assisted by the 
frequent branching and consequent increasing density 
hindering their horizontal extension. This closeness of 
growth, too, shutting off the light, causes the death of all 
the interior leaves and many of the stems, so that only the 
stouter persist, the interspaces becoming filled, in the case 
of the thicker cushions, with peat, and in that of the 
patches and low cushions with wind-blown silt. According 
to the relation between the rate of horizontal spread and 
vertical growth are patch-plants or cushions produced. 
The leaves are small, generally more or less imbricating, 
and very frequently tomentose. The ultimate shoots are 
sometimes pressed so closely together that they form a 
hard and unyielding surface, as in the case of the various 
“ vegetable-sheep ” (R. eximia, R. Goyeni, etc.). When large 
quantities of peat (raw humus) are stored up within the 
cushion, the upper branches put forth adventitious roots by 
means of which the plant gets most of its water and salts, 
the main root serving chiefly as an anchor. 
Raoulia Haastii, the most important species of the sub- 
alpine river-beds of much of the Canterbury and Westland 
Southern Alps, forms bright green cushions of consider- 
able dimensions, that shown in the photograph (Plate X.) 
measuring 68x57 cm. There is a stout, woody main 
stem and branches. The leaves are crowded near the ends 
of the ultimate branchlets, the leafy part of the shoot being 
about 9 mm., or even less, in length. They are glabrous, 
coriaceous, and the base is sheathing; the sides of the blade 
are bent upwards, making the upper surface concave. A 
cross-section of the cushion shows a very narrow green 
zone of living leafy shoots, a second rather wider brown 
zone of stems with dead leaves attached, a third 4-5 cm. 
deep or more, with many of the branches and leaves 
turned into peat, but not fallen away, a fourth where 
the peat has fallen away from the stems and where the 
